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2021 Fall Meeting

Functional materials


Emergent functional materials with respect to extreme conditions

The functional materials with quantum emergent phenomena manifest profound phenomena, defining the current frontiers of condensed mattes. They cover the multiple spin, charge, and/or orbital interactions in the matrix of crystal lattices and display properties such as superconductivity, diluted magnetic semiconductor properties, and topological quantum phenomena, promising for applications.


The main scope will be focused on recent new emergent materials including superconductors, diluted magnetic semiconductors, topological ordered materials with respect to extreme conditions such as high pressure, low temperature or high magnetic fields, etc. The extreme conditions can be very effective in changing atomic distance, enhancing orbital overlap, and consequently modifying crystalline structures and tuning interactions or multiple couplings. One can thus realize novel materials states.

It is very well established that each material will usually undergo tens of phase transitions over the Mbar pressure range, strongly implying that high pressure could generate plenty of new states of materials. Hence high pressure is considered to be a powerful tool to develop novel condensed states. Pressure provides a new dimension for the study of quantum emergent compounds. Quantum emergent phenomena will have totally new critical relationships if one investigates the pressure dimension together with the usual temperature and composition parameters. More recently it has been shown that pressure variations stimulate dramatic enhancements of the Tc of superconductors. Pressure generally can drive the insulator-metal transition due to the band widening, overlapping effects, and the redistribution and transformation of outer shell electrons upon shortening the atomic distance. More important is that high pressure tends to stabilize novel compounds or states that otherwise could hardly obtained by conventional means. Using high pressure advantages to synthesize and study hydrides, borides or nitrides etc. is not only of industrial interest but also important for developing high pressure science itself since those low Z compounds are theoretically easier to analyse. Nevertheless pressure is a unique and irreplaceable probe to check and develop theoretical model. For instance, pressure can substantially modify the electron correlation and e-p interaction, the spin orientation, giving rise to superconductivity in conventional materials such as theoretically predicated metallic hydrogen. The delocalization tendency under pressure leads many insulators, semiconductors and molecular crystals to become metals that cover huge scope of emergent materials.

Hot topics to be covered by the symposium:

  • Novel technologies to fabricate nano-materials
  • Multifunctional materials
  • Interface-based new or enhanced properties
  • Materials for flexible electronics
  • Proximity effects
  • Interfaces between 2D materials
  • Interfaces involving topologically protected states
  • High-temperature superconductors
  • Diluted magnetic semiconductors
  • Topological ordered materials
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08:30 Welcome message and introduction to the Symposium    
High Pressure 1 : tba
Authors : Yoshihiro Kubozono, Tomoya Taguchi, Mitsuki Ikeda, Hidenori Goto and Ritsuko Eguchi
Affiliations : Research Institute for Interdisciplinary Science, Okayama University, Okayama 70-8530, Japan

Resume : The superconducting material, Ba0.77Na0.23Ti2Sb2O, was investigated to depict the phase diagram of superconducting transition temperature (Tc) against pressure (p). It showed a Tc value of 5.8 K at ambient pressure. The value of Tc decreased with pressure below 8 GPa, while it rapidly increased above 8 GPa and slowly decreased with pressure above 11 GPa. Namely, a high pressure superconducting phase emerged above ~9 GPa. The X-ray diffraction of Ba0.77Na0.23Ti2Sb2O was also investigated at 0 – 22.0 GPa, demonstrating the structural transition at around 9 GPa. Thus, an obvious relation between the crystal structure and the superconductivity was revealed, indicating the emergence of new superconducting phase induced by structural phase transition. We are now investigating pressure dependence of crystal structures and superconducting properties of BaTi2(Sb1-yBiy)2O at y = 0 – 1.0; these compounds are of significance from physical point of view because of the observation of CDW / SDW transition at around y = 0 and the feature of Dirac semimetal at y = 1.0. Moreover, the superconducting properties of topological insulator Sb2Te3-ySey were investigated over a wide pressure range, i.e., the relation between structure and superconducting properties was elucidated.

Authors : Kuo Li
Affiliations : Center for High Pressure Science &Technology Advanced Research, Beijing, China

Resume : High-pressure synthesis is widely applied in the exploration of novel materials. Traditionally, high temperature is often coupled with high pressure to accelerate to reaction. On the other hand, under room temperature or even low temperature, more meta-stable carbon-based materials can be obtained through topo-chemical reactions of unsaturated molecular crystals. Through crystallographic and theoretical investigations, we conclude that the unsaturated molecules in these pressure-induced polymerizations have critical distances for intermolecular bonding. The distance is related to the bond type, charge, and geometry of the reactant, as well as the bonding routes. Among these routes, Dehydro-Diels-Alder reaction is the most promising one to construct carbon-based material under relatively low pressure.

Authors : Runze Yu1,2、Jianfa Zhao1、Xubin Ye1、Youwen Long1、Changqing Jin1
Affiliations : 1Institute of Physics, Chinese Academy of Sciences 2 University of Science and Technology of Beijing

Resume : Pressure is a key parameter, like temperature and composition, to determine the states of materials. The materials demonstrate a variety of structures and physical properties under pressure. Perovskite structure is an important carrier of functional materials, such as high temperature superconductivity, Giant Magnetoresistance and perovskite solar cells et al. This structure is dense packed and many of perovskite and related compounds can only exist under high pressure. So high pressure is a powerful tool to discovery and fabricate new perovskite and related compounds. In this talk, first I will give a short introduction about the merit of high pressure in researching new perovskite compounds. Then I will focus on our recent progress on the perovskite related functional materials: PbHg3Ti4O12, a combinatory ferroelectric compound bridging simple ABO3 and A-site-ordered quadruple perovskite1; Observation of novel charge ordering and spin reorientation2 in perovskite oxide PbFeO3. Finally I will give a brief comment and make a prospect of our research. Key Words:High Pressure;Perovskite;Ferroelectricity;Spin Reorientation Reference: 1. Jianfa Zhao et al. A combinatory ferroelectric compound bridging simple ABO3 and A-site-ordered quadruple perovskite, Nature Commu. 12, 1-11 (2021). 2. Xubin Ye et al. Observation of novel charge ordering and spin reorientation in perovskite oxide PbFeO3, Nature Commu. 12, 1-9 (2021).

Authors : Xiang Li
Affiliations : Beijing Institute of Technology

Resume : A great deal of interest has been focused on new functional materials, because there is a rich variety of intriguing phenomena such as multiferroicity, high-temperature superconductivity and colossal magnetoresistance due to strong correlations among lattice dynamics, charges, spins and orbitals. Pressure as one of the basic thermodynamic parameters influences crystal structures so as to control magnetic and transport properties. We have synthesized a series of new functional materials under high pressure and studied their physical properties by fully comprehensive measurements, which helps to clarify a few fundamental questions and provide a roadmap for developing new functional materials.

10:30 Q&A Session / Break    
High Pressure 2 : tba
Authors : F. Mila
Affiliations : Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne Switzerland

Resume : Since the discovery of its first magnetization plateaus in 1999, the quasi-2D compound SrCu2(BO3)2 has been the focus of considerable and uninterrupted activity, first in very intense magnetic fields, then in high pressure, and more recently combining both. Its (P,H) phase diagram is amazingly rich, with about 20 phases including a remarkable sequence of fractional magnetizations plateaus at 1/8, 2/15, 1/6, 1/4, 1/3, 2/5 and 1/2 at ambient pressure in fields up to 110 Tesla, an intermediate plaquette phase at 20 kbar before antiferromagnetic order develops under pressure around 26 kbar, and new phases when combining both field and pressure, among which a 1/5 plateau and a spin-supersolid. All these phases are one way or the other consequences of the very special orthogonal arrangement of spin-1/2 dimers inside the layers, also known as the Shastry-Sutherland lattice, whose ground state at zero field and for parameters corresponding to ambient pressure is a simple product of dimer singlets. This zero-temperature phase diagram could be understood thanks to the development of advanced numerical approaches, in particular tensor-network algorithms. Finally, the thermal properties are also very exciting, with in particular the discovery of a critical point analogous to that of water at the transition between the dimer phase and the plaquette phase.

Authors : Ryotaro Arita
Affiliations : 1Department of Applied Physics, University of Tokyo, 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656, Japan, 2RIKEN Center for Emergent Matter Science, 2-1 Wako Hirosawa, Saitama 351-8656, Japan

Resume : We formulate an efficient scheme to perform Migdal-Eliashberg calculation considering the retardation effect from first principles. While the conventional approach based on the McMillan-Allen-Dynes formula introduces the empirical parameter * (the pseudo Coulomb potential), we show that the intermediate representation of the Green's function [1] dramatically reduces the numerical cost and enables us to solve the linearized gap equation without using any empirical parameters [2]. We then apply this method to H3S, LaH10, and carbon-doped H3S and calculated their superconducting transition temperatures (Tc’s). We show that the calculated Tc’s agree well with the experiments for H3S and LaH10 [3,4,5,6,7]. While room temperature superconductivity has been reported for carbonaceous sulfur hydride [8], we show that the calculated Tc of carbon-doped H3S is much lower than the experimental value [9]. References: [1] H. Shinaoka et al., Phys. Rev. B 96, 035147 (2017). [2] T. Wang, Phys. Rev. B 102, 134503 (2020). [3] A.P. Drozdov et al., Nature 525, 73 (2015). [4] M. Somayazulu et al., Phys. Rev. Lett. 122, 027001 (2019). [5] A.P. Drozdov et al., Nature 569, 528 (2019). [6] W. Sano et al., Phys. Rev. B 93, 094525 (2016). [7] I. Errea et al., Nature 578, 66 (2020). [8] E. Snider et al., Nature 586, 373 (2020). [9] T. Wang et al., arXiv:2014.03710

Authors : Martin Rahm
Affiliations : Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Sweden.

Resume : This presentation highlights the use of atomic properties to rationalize chemistry under conditions of high pressure. A quantum mechanical model that can describe the effect of uniform compression of single atoms by a nonreactive chemical medium is presented. Several characteristics, which are important for rationalization of structure and bonding under ambient conditions, are extended up to 300 GPa for 93 atoms: (1) ground state electronic configuration of atoms; (2) electronegativity; and (3) Van der Waals radii. Comparison with experimental equations of state and structure will be discussed along with predictions of inversed polarity and reactivity under compression. An open interactive web application, the Atoms Under Pressure Database, will be demonstrated.

Authors : Jinlong Zhu1,2*, Meiling Jin1,2†, Guangtong Liu3, Zheng Liu4,5,
Affiliations : 1Department of Physics & Shenzhen Engineering Research Center for Frontier Materials Synthesis at High Pressures, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China 2Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing, 100094, China 3Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China 4School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore 5School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.

Resume : The unique electronic structure and crystal structure driven by external pressure in transition metal tellurides (TMTs) can host unconventional quantum states. Here we report the discovery of pressure-induced dome-shaped superconducting phase in type-II Weyl semimetal candidate NbIrTe4. We propose that the emergence of superconductivity in NbIrTe4 can be attributed to the phase transition from the ambient Td-phase to a monoclinic 1T-phase through a sliding of the NbIrTe4 layers. This phase transition introduces an inversion center and eliminates the topological Weyl fermions of Td-phase. Strikingly, we found an anisotropic transport in the vicinity of the superconducting state, suggesting the emergence of a “stripe”-like phase. The dome-shaped superconducting phase and anisotropic transport are possibly due to the spatially modulated interlayer Josephson coupling strength, which suggests quasi two-dimensional superconductivity in NbIrTe4. It is critical important to measure the exfoliated single layered NbIrTe4 to further confirm this proposal. Key words: Superconductivity, anisotropic transport, phase transition, high pressure.

13:00 Q&A Session / Break    
High Pressure 3 : tba
Authors : Hiroki Takahashi1, Yuto Kikuchi1, Chizuru Kawashima1, Kouhei Ishida1, Hayato Kamioka1, Kohei Yoshimatsu2, Takuto Soma3, Akira Ohtomo3
Affiliations : 1Nihon University, Tokyo,156-8550, Japan, 2Tohoku University, Sendai, 980-8577, Japan, 3Tokyo Institute of Technology, 152-8552, Japan

Resume : Many kinds of titanate have been studied in basic and industrial science. Among the titanates, superconductivity was discovered in TiO of NaCl type with Tc = 2.3K 1) and rather high-Tc tinanate was discovered in the spinel compound Li1+xTi2-xO4 with Tc =13 K 2). Inspired by the discovery of high- Tc cuprate, titanates including a light element have been extensively studied as a high- Tc candidate. Among the titanates, Ti4O7 is known as the first member of Magnéli phase, which has TinO2n-1 formula and low-dimensional structure having shear planes and metal-insulator transition (MIT) was reported at ~150 K, in which it was indicated that the transition is related to the mobility of bipolaron formed by the strong electron-phonon interaction. Although the MIT completely disappeared only in case of application of pressure above 3 GPa, superconductivity could not be observed in the pressure range to 8 GPa. In 2017, Ti4O7 and -Ti3O5 epitaxial films were reported to exhibit superconductivity with Tc = 3.0 K and 7.1 K, respectively3). Around the same time, TiO epitaxial film was reported to show superconductivity with Tc = 7 K,4) which is higher than the case of the TiO bulk, and orthorhombic Ti2O3 film was reported to be a superconductor with Tc = 8 K5). In this study, high-pressure electrical resistance measurements were carried out for epitaxial Ti4O7 film to contribute the understanding of the mechanism of superconductivity observed in Ti4O7 film. Hydrostatic pressure was applied by a piston-cylinder device up to 2.5 GPa6), using Daphne oil 7474 as a pressure-transmitting medium (PTM). Pressure was changed only at room temperature, where the PTM is liquid. From electrical resistance measurements, the MIT temperature (TM-I) increased with a rate of 15 K/GPa and Tc decreased with a rate of -0.7 K/GPa with increasing pressure for Ti4O7 film. These results suggest that the carrier concentration decreases with applying pressure. On the other hand, the opposite pressure dependence of Tc and TM-I was observed for Ti4O7 film using Fluorinert 70/77 as a PTM above ~1 GPa at which it shows solidification. It is thought that the solidification of liquid generates the anisotropic stress to the Ti4O7 film. These results suggest that the electronic state in the Ti4O7 film is very sensitive to strain and existing on the subtle balance under compressive or tensile strain in the film. It is exhibited that the suppression of bipolaronic state is advantageous to the emergence of superconducting state for several kinds of Ti4O7 film 7). Measurements using strain gauge to characterize the strain distribution is underway and the results will be presented. References: 1) N. J. Doyle et al., Phys. Lett. 26A, 604 (1968). 2) Y. Ueda et al., J. Solid State Chem. 77, 401 (1988). 3) K. Yoshimatsu., Sci. Rep. 7, 12544 (2017). 4) C. Zhang et al., npj Quantum Materials 2, 2 (2017). 5) Y. Li et al., NPG Asia Materials 10, 522 (2018). 6) S. Sekiguchi et al., J. Phys. Soc. Jpn., 88, 035001 (2021). 7) T. Soma et al., J. Phys. Soc. Jpn., 90, 023705 (2021).

Authors : K. Horigane1, M. Fujii2, S. Kidokoro3, H. Okabe4, K. Kobayashi1,2, R. Horie1, H. Ishii5, Y. F. Liao5, Y. Kubozono1, A. Koda4, K. Simizu3, R. Kadono4, and J. Akimitsu1
Affiliations : 1 Research Institute for Interdisciplinary Science Okayama Univ. Okayama, Japan 2Graduate School of Natural Science and Technology, Okayama Univ., Okayama, Japan 3KYOKUGEN Osaka Univ., Osaka, Japan 4Institute of Materials Structure Science/J-PARCCENTER, KEK, Ibaraki, Japan 5National Synchrotron Radiation Research Center, Hsinchu, Taiwan

Resume : The 5d transition-metal compounds have been attracting intensive attention in recent years because their strong spin–orbit coupling (SOC) leads to novel physical properties. For instance, Sr2IrO4 (TN = 240K) is a novel Jeff = 1/2 Mott state induced by relativistic SOC and Coulomb repulsion U [1]. Theoretically, Sr2IrO4 was predicted to be a high-temperature superconductor when doped with carriers because it strongly resembles the cuprates in crystal structure, electronic structure, and magnetic coupling constants [2]. Because of the similar Mott physics between cuprates and iridates, Sr2IrO4 is a good candidate for exploring unconventional high-Tc superconductivity by carrier doping. Experimentally, electron doping was realized in Sr2IrO4 by La substitution, oxygen deficiency, or surface K doping. A unique electronic state such as d-wave gapped state and in-gap state was found in the electron doped regime by angle-resolved photoemission spectroscopy (ARPES) [3,4], resembling the underdoped cuprates. However, no experimental evidence of superconductivity has been found up to now. In this presentation, we present our recent carrier doping and high-pressure studies in Sr2-xLaxIrO. The magnetic transition temperature TN and electrical resistivity decreased with increasing La doping, consistent with previous studies involving single-crystalline samples. We succeeded in making 15% electron doping samples in Sr2-xLaxIrO4. However, non-metallic behavior was found in this system. In order to understand how the electron carriers affect the magnetic state and understanding the microscopic doping mechanism of Sr2-xLaxIrO4 system, we performed μSR experiment of Sr2-xLaxIrO4 in a wide electron doping region. Interestingly, we found two fractions of long-range order phases in the lightly electron doping region (x< 0.03). The effective Ir moment of type A magnetic phase is ~0.4μB corresponding to the non-doped Sr2IrO4 phase, while that of type B is 0.1μB at x=0.015. The volume fractions of the two different state estimated are 57% (type B) and 8.2% (type A), respectively. This result indicates that magnetic phase separation is realized even in the lightly electron doping region. On the other hand, the time spectra of highly electron doping region (x=0.15) can be fitted well by simple exponential function, suggesting magnetic phase is paramagnetic. To realize the superconducting state in this system, we studied electronic transport properties of highly electron doped Sr2-xLaxIrO4 by measuring the electrical resistivity under high pressure. Although no definitive signatures of a pressure-induced metallic state have been found in Sr2IrO4 up to 55GPa [5], a clear metal-insulator transition was occurred in single crystal samples of Sr1.92La0.08IrO4 at 14.7GPa. Resistivity decreased with increasing pressure and lowest resistivity was realized at 18GPa. However, resistivity starts to increase above 18GPa and superconducting behavior was not found in this system. Reference [1] B. J. Kim et al., Phys. Rev. Lett. 101, 076402 (2008)[2] H. Watanabe, T. Shirakawa and S. Yunoki, Phys. Rev. Lett. 110, 027002 (2013).[3] Y. K. Kim et al., Nat. Phys. 12, 37 (2016)[4] K. Terashima et al., PRB 96, 041106 (R) (2017)[5] D. A. Zocco et al., J. Phys.:Condens. Matter 26, 255603 (2014)

Authors : Dariusz Jakub Gawryluk1, Yannick Maximilian Klein1, Mirosław Kozłowski2, Philippe Lacorre3, Anthony Linden4, Marisa Medarde1
Affiliations : 1 Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland, 2 Łukasiewicz Research Network Tele & Radio Research Institute, 11 Ratusznowa Street, 03-450 Warsaw, Poland, 3 Institut des Molécules et Materiaux du Mans (IMMM) – UMR 6283 CNRS, Le Mans Université, Avenue Olivier Messiaen, 72085 Le Mans, France, 4 Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland

Resume : The rare earth nickelates (RNiO3) are a model example of strongly correlated electron materials. The most notable characteristic of those compounds is the presence of spontaneous, temperature-driven metal-to-insulator transitions at temperatures that systematically change with size of R ionic radii from 130 K (R = Pr) to 600 K (R = Lu) [1]. Since that transition happens in absence of Ni mixed valence or chemical disorder, nickelates are perfect, extremely clean model systems for the investigation of the boundary between localized and itinerant behaviour in theoretical studies. Although the existence of the spontaneous electronic localization in RNiO3 has been known since 1991 [2], it is unclear how electronic correlations, lattice, and magnetic degrees of freedom interplay and lead to the gap opening. In addition, other interesting phenomena such as an unusual non-centrosymmetric antiferromagnetic ordering [3], superconductivity [4] or multiferroicity [5] have been either observed or theoretically predicted. An important drawback for the advancement in the understanding of the complex physics of RNiO3 has been limited by their challenging chemistry, which requires the use of high-pressure and high-temperature during synthesis. Here will be presented the first successful growth of RNiO3 single crystals with sizes up to ~100 μm, achieved by applying the solvothermal method in temperature gradient under 2000 bar of oxygen pressure [6]. Results of detailed structural and physical property characterization illustrating the excellent quality of the obtained bulk crystals will be discussed. This work was supported by the Swiss National Science Foundation through the NCCR MARVEL (Grant No. 51NF40-182892), and the R’equip Grant n. 461 206021_139082. [1] Gawryluk, D. J. et al., (2019). Phys. Rev. B 100, 205137. [2] Lacorre, Ph. et al., (1991). J. Solid State Chem. 91, 225. [3] Alonso, J. A. et al., (1999). Phys. Rev. Lett. 82, 3871. [4] Chaloupka, J. et al., (2008). Phys. Rev. Lett. 100, 016404. & Li, D. et al., (2019). Nature 572, 624. [5] Giovannetti, G. et al., (2009). Phys. Rev. Lett. 103, 156401. & Perez-Mato, J. M. et al., (2016). J. Phys.: Condens. Matter 28 286001. & Ardizzone, I. et al., (2021). Phys. Rev. Research 3, 033007. [6] Klein, Y. M. et al., (2021). Cryst. Growth Des. 10.1021/acs.cgd.1c00474.

Authors : Huan Li, Hidenori Goto, Ritsuko Eguchi, and Yoshihiro Kubozono
Affiliations : Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan

Resume : The structural and superconducting properties of alkali-Bi based compounds, KBi2 and RbBi2, were fully investigated over a wide pressure range. The samples of KBi2 and RbBi2 were prepared by use of a liquid ammonia (NH3) technique, which provided the superconducting transition temperatures, Tc’s, of 3.50 and 4.21 K at ambient pressure. The KBi2 sample decomposed into KBi and Bi by an application of pressure up to ~9 GPa, as indicated from X-ray diffraction patterns, and the RbBi2 sample also decomposed above ~9 GPa. Moreover, the discontinuous change of Tconset for KBi2 was observed at ~9 GPa, which seems to reflect the decomposition of KBi2 into KBi and Bi. Here, we suggested that the superconducting phase above 9 GPa might not be ascribed to KBi2 but KBi, because the XRD peaks was assigned to KBi above 9 GPa. Thus, the superconducting properties and stability of alkali-Bi compounds under pressure were systematically explored in this study. It was suggested from magnetic field dependence of Tc’s of KBi2 and RbBi2 under pressure that the superconducting Cooper pair symmetry might not be so simple i.e., the possibility of spin triplet p-wave pairing (topological nontrivial) was suggested for KBi2 and RbBi2.

Authors : Ai Suzuki, Hidenori Goto, Ritsuko Eguchi, Yoshihiro Kubozono
Affiliations : Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan

Resume : A new type of topological insulator, PdBi2, has been extensively investigated, which exhibits two different crystal phases, i.e., -PdBi2 and -PdBi2, both of which are topological insulators. These phases provided superconductivity at the Tc of 1.7 K for -PdBi2 [1] and the Tc of 4.25 K for -PdBi2 [2]. In this study, we fully investigated the crystal structure and superconducting properties of β-PdBi2 under pressure. The powder XRD patterns at 0 - 22.0 GPa indicate no structural phase transitions, and the unit cell volume, V, shrinks monotonically with pressure, which is different from the behavior of V against pressure in α-PdBi2. The temperature dependence of electrical resistance was studied at 0 - 11.8 GPa, and the value of Tc is almost constant at ~4.4 K. The elucidation of pairing mechanism of β-PdBi2 was attempted at ambient pressure and 10.7 GPa [4]. Moreover, we are now attempting to synthesize new PdBi2 families through doping with Pt and Sb. The -Pd1-xPtxBi2 sample showed the onset value of superconducting transition, Tconset, of 5.02 K, which is higher than that of -PdBi2 (Tc = 1.7 K). [1] Y. Zhou et al. Phys. Rev. B 99, 054501 (2019). [2] K. Zhao et al. Phys. Rev. B 92, 174404 (2015) [3] G. Pristᨠet al. Phys. Rev. B 97, 134505 (2018) [4] A. Suzuki et al. J. Phys.: Condens. Matter 33, 135702 (2021).

16:00 Q&A Session    
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Superconductors 1 : tba
Authors : Hongli Suo
Affiliations : Key Laboratory of Advanced Functional Materials, Ministry of Education, Faculty of Material and Manufacturing, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100124, China

Resume : During past years, the superconducting material has run to its eve of the large scale applications. In this talk, I will present the state of the art of 2G-HTS tape and relevant key science and technical issues worldwide. Firstly, the various methods of fabricating 2G-HTS tapes and their current status at home and abroad will be summarized, then I will introduces the key processing technologies in the preparation of long tapes, including the technical routes, substrate development as well as artificial flux pinning in the superconducting films. Finally the power applications, especially in the field of HTS magnet will be mentioned.

Authors : Jianting Ye
Affiliations : Device Physics of Complex Materials, Zernike Institute for Advanced Materials, University of Groningen

Resume : Many recent discoveries on novel electronic states were made on 2D materials. Especially, by making artificial bilayer systems, where new electronic states such as superconductivity and ferromagnetism have been reported. This talk will discuss quantum phase transitions and Ising superconductivity induced in 2D transition metal dichalcogenides. Using ionic gating, quantum phases such as superconductivity can be induced electrostatically on many 2D materials. In transition metal dichalcogenides, Ising-like paring states can form on the unique electronic structure shown in Fig. 1 [1,2]. Also, we will discuss how to couple two Ising superconducting states through Josephson coupling by inducing superconductivity symmetrically in a suspended bilayer. This method can access electronic states with broken local inversion symmetry while maintaining the global inversion symmetry [3]. Controlling the Josephson coupling and spin-orbit coupling is an essential step for realizing many exotic electronics states predicted for the coupled bilayer superconducting system with strong spin-orbit interactions. References [1] Lu, J. M. Zheliuk O, et al., Science 350 1353 (2015). [2] Lu, J. M. Zheliuk O, et al., Proceedings of the National Academy of Sciences 115 3551 (2018). [3] Zheliuk O, Lu, J. M., et al., Nature Nanotechnology 14 1123 (2019).

09:30 Q&A Session / Break    
Superconductors 2 : tba
Authors : Fabian von Rohr
Affiliations : Department of Chemistry, University of Zurich, CH-8057 Zürich, Switzerland

Resume : The upper critical field is a fundamental measure of the strength of superconductivity in a material. It is also a cornerstone for the realization of superconducting magnet applications. The critical field arises because of the Copper pair breaking at a limiting field, which is due to the Pauli paramagnetism of the electrons. The maximal possible magnetic field strength for this effect is commonly known as the Pauli paramagnetic limit given as 0HPauli ≈ 1.86 [T/K] ∙ Tc for a weak-coupling BCS superconductor. The violation of this limit is only rarely observed. Exceptions include some low-temperature heavy fermion and some strongly anisotropic superconductors. In this presentation, we will discuss the superconductivity at 9.75 K in the centrosymmetric, cubic -carbide-type compound Nb4Rh2C1-. We find that this material has a remarkably high upper critical field of 0Hc2 ≈ 28.5 T, which is exceeding by far its weak-coupling BCS Pauli paramagnetic limit of 0HPauli ≈ 18.1 T. We will discuss possible origins and consequences of these extremely large magnetic fields in this material and compare it to other -carbide superconductors.

Authors : A. Shengelaya1,2, F. La Mattina3, K. Conder4, K. A. Müller5
Affiliations : 1Department of Physics, Tbilisi State University, Tbilisi, Georgia 2Andronikashvili Institute of Physics, Tbilisi State University, Tbilisi, Georgia 3Laboratory for Transport at Nanoscale Interfaces, Empa Swiss Federal Laboratories for Science and Technology, Dübendorf, Switzerland 4Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, Villigen PSI, Switzerland 5IBM Research - Zürich, Rüschlikon, Switzerland

Resume : Despite exciting developments in the field of superconductivity over a period of three decades, cuprates remain the only materials which exhibit superconductivity above the liquid nitrogen boiling temperature at ambient pressure. Here we report results of the search for a possible superconducting state in tungsten oxides WO3-x in a wide range of oxygen deficiency 0< x< 1. In some samples with composition WO2.9 the signatures of superconductivity with the transition temperature Tc = 80 K were registered by means of magnetization measurements. The variation of resistivity with temperature in this compound also displays unusual features, such as a broad maximum around 230 K and a logarithmic increase of resistivity at low temperatures. In contrast to magnetization data, superconducting transition below Tc = 80 K is not detected in resistivity measurements. This indicates that the superconductivity is localized in small regions that do not percolate. A strong increase of positive magnetoresistance (MR) was found below 80 K. This effect is very similar to that observed in underdoped cuprates, where the substantial increase of MR was attributed to superconducting fluctuations in small clusters. Therefore the temperature dependence of MR supports the presence of non-percolating superconducting clusters in WO2.9 below 80 K in agreement with magnetization data. As a further avenue of research, it is especially promising to study pressure effects on normal and superconducting properties of oxygen reduced tungsten oxides. By applying hydrostatic or uniaxial pressure, one can tune the band structure and coupling between crystallographic shear planes, where superconducting regions are presumably localized. It is expected that by improving the coupling and percolation between superconducting clusters, bulk superconductivity and zero resistance state might be achieved.

12:00 Q&A Session / Break    
New Materals 1 : tba
Authors : Bo Gu
Affiliations : Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China

Resume : Combining magnetism and semiconductor enables the development of magnetic semiconductors, a promising way to realize spintronic applications based on the use of both charge and spin degrees of freedom. For the classic diluted magnetic semiconductor (DMS) (Ga,Mn)As, its highest Curie temperature Tc is about 200 K, still far below room temperature. One way to solve this problem is to develop the diluted magnetic semiconductors with match doping. Here, we propose a method to realize DMS with p- and n-type carriers by choosing host semiconductors with narrow band gaps [1]. By density function theory and quantum Monte Carlo simulation, we demonstrate such semiconductors using Mn-doped BaZn2As2, which has a band gap of 0.2 eV. In addition, the Tc in Mn-doped BaZn2Sb2 is predicted to be higher than Tc = 230K in Mn-doped BaZn2As2 in the recent experiment. We also predict the DMS Cr-doped BaZn2As2 with stable ferromagnetism in p- and n-type carriers [2]. Our results show that the origin of high Tc in (Ga,Fe)Sb and (In,Fe)Sb is not due to the carrier induced mechanism because Fe3+ does not introduce carriers, and predict the DMS Cr-doped InSb, InAs, and GaSb wtih possibly high Tc [3]. Another solution is to develop two-dimensional Van der Waals ferromagnetic semiconductors. By density-functional-theory calculations, we predict several stable two-dimensional (2D) Van der Waals ferromagnetic semiconductors with high Tc, including strain-induced 2D room-temperature ferromagnetic semiconductor Cr2Ge2Se6 [4], 2D room-temperature ferromagnetic semiconductors PtBr3 and PdBr3, that could exhibit a high-temperature quantum anomalous Hall effect [5], 2D ferromagnetic semiconductors TcSiTe3, TcGeSe3, and TcGeTe3 with high Tc around 200–500 K [6], 2D Janus semiconductor Fe2Cl3I3 with both spin and charge polarizations and the highly sensitive strain-controlled magnetic states [7], 2D two-dimensional magnetic semiconductor heterostructure Cr2Ge2Te6/PtSe2 with enhanced Tc above room temperature [8], 2D Kagome magnetic semiconductors Co3Pb3S2, Co3Pb3Se2, Co3Sn3Se2 with quantum anomalous Hall effect with high Chern number and large band gap [9], and 2D magnetic semiconductors MnBi2Te4, MnBi2Se2Te2, MnBi2S2Te2 with electric field induced topological phase transition and large enhancements of spin-orbit coupling and Curie temperature [10]. Reference: [1] B. Gu and S. Maekawa, Phys. Rev. B 94, 155202 (2016). [2] B. Gu, and S. Maekawa, AIP Advances 7, 055805 (2017). [3] J. Y. You, B. Gu, S. Maekawa, and G. Su, Phys. Rev. B 102, 094432 (2020). [4] X. J. Dong, J. Y. You, B. Gu, and G. Su, Phys. Rev. Applied 12, 014020 (2019). [5] J. Y. You, Z. Zhang, B. Gu, and G. Su, Phys. Rev. Applied 12, 024063 (2019). [6] J. Y. You, Z. Zhang, X. J. Dong, B. Gu, and G. Su, Phys. Rev. Research 2, 013002 (2020). [7] Z. Zhang, J. Y. You, B. Gu, and G. Su, J. Phys. Chem. C 124, 19219 (2020). [8] X. J. Dong, J. Y. You, Z. Zhang, B. Gu, and G. Su, Phys. Rev. B 102, 144443 (2020). [9] Z. Zhang, J. Y. You, X. Y. Ma, B. Gu, and G. Su, Phys. Rev. B 103, 014410 (2021). [10] J. Y. You, X. J. Dong, B. Gu, and G. Su, Phys. Rev. B 103, 104403 (2021).

Authors : Michael A. Hayward
Affiliations : Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom

Resume : The vast majority of complex solids are prepared at high temperatures under reaction conditions that apply ‘thermodynamic control’ to the selection of reaction products. By utilizing the ‘extreme chemical conditions’ of low-temperature, and very low pO2 it is possible to prepare a range of novel solids which are metastable and cannot be synthesised under more conventional conditions. By using these synthetic approaches it is possible prepare extended solids containing transition metal cations with unusual combinations of oxidation state and coordination geometry (e.g. square-planar Ni1+, Fe2+, Ru2+, Ir2+). In addition, these conditions can also facilitate the substitution of oxide anions by hydride anions, to form transition-metal oxyhydride phases. The differing charges of O2- and H- mean that any hydride-for-oxide anion exchange is necessarily reductive. Furthermore, the greater polarizability in combination with the lower electronegativity of hydride anions means that M-H bonds have a greater degree of covalency and orbital mixing than the corresponding M-O bonds, and as a result the band structures of oxide-hydride phases are qualitatively different to all-oxide systems, and the strength of magnetic exchange couplings is also enhanced. A further, more subtle, difference between oxide and hydride is the lack of π-symmetry valence orbitals in the later anion. This means that hydride ions cannot be involved in bond formation with metal orbitals of π-symmetry. This can have a dramatic influence on the orbital connectivity of oxide-hydride phases, particularly when there is extensive anion order, as can be seen in the highly 2-dimensional character of the transport in the high-pressure metallic state of SrVO2H. The structures and physical properties of a range of novel 3d and 3d/4d reduced transition-metal oxides and oxyhydrides will be described.

Authors : Anatoly B. Belonoshko1,2, Jie Fu3, and Grigory Smirnov4,5
Affiliations : 1Condensed Matter Theory, Department of Physics, AlbaNova University Center, Royal Institute of Technology (KTH), Stockholm, Sweden; e-mail: 2Department of Physics, University of South Florida, Tampa, FL, USA 3Department of Physics, School of Physical Science and Technology, Ningbo University, Ningbo, China 4HSE University, Russian Federation 5Joint Institute for High Temperatures of the Russian Academy of Sciences, Moscow, Russian Federation

Resume : When computing phase diagram from first principles, one might need to simulate prohibitively large supercells. These supercells can be modelled using atomistic models of interactions. However, these models do not allow an explicit treatment of electronic subsystem which might be important in metallic systems at high temperature. The solution to this is a hybrid method, where the free energy of the ionic subsystem is computed by thermodynamic integration for the interatomic potential and then corrected for the electronic entropy term of the electronic subsystem. We apply this method to iron phase diagram at high pressure and temperature and demonstrate good agreement with pure ab initio method for the equilibria that do not require large number of atoms and with the experiment where large number of atoms is critical. The computed phase diagram is of large practical value.

16:00 Q&A Session / Break    
Poster Session : tba
Authors : Jianfa Zhao, Wenmin Li, Runze Yu, & Changqing Jin
Affiliations : Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.

Resume :   The simple ABO3 and A-site-ordered AA’3B4O12 perovskites represent two types of classical perovskite functional materials. There are well-known simple perovskites with ferroelectric properties, while there is still no report of ferroelectricity due to symmetry breaking transition in A-site-ordered quadruple perovskites. Here we report the high pressure synthesis of an Asite- ordered perovskite PbHg3Ti4O12, the only known quadruple perovskite that transforms from high-temperature centrosymmetric paraelectric phase to low-temperature non-centrosymmetric ferroelectric phase. The coordination chemistry of Hg2+ is changed from square planar as in typical A-site-ordered quadruple perovskite to a rare stereo type with 8 ligands in PbHg3Ti4O12. Thus PbHg3Ti4O12 appears to be a combinatory link from simple ABO3 perovskites to A-site-ordered AA’3Ti4O12 perovskites, sharing both displacive ferroelectricity with former and structure coordination with latter. This is the only example so far showing ferroelectricity due to symmetry breaking phase transition in AA’3B4O12-type A-siteordered perovskites, and opens a direction to search for ferroelectric materials.

Authors : M. Lungu1, C. Staicu1, 2, O. G. Pompilian1, B. Butoi1, A. Marin3, F. Baiasu1, 2, D. Cristea4 and C. Porosnicu1
Affiliations : 1 National Institute for Laser, Plasma and Radiation Physics, 077125, Magurele, Romania; 2 Physics Department, University of Bucharest, 077125, Magurele, Romania; 3 Institute for Nuclear Research Pitesti, POB 78, Mioveni, Arges, Romania; 4 Faculty of Materials Science and Engineering, Transilvania University, 500068, Brasov, Romania;

Resume : In the last decade, the fusion research community presented high interest in studying candidate materials and deposition techniques applicable for the fabrication of permeation barriers which are intended to minimize the nuclear fuel permeation/inventory and corrosion. The R&D motivation arises from the necessity of the future fusion reactors as Demonstration Power Station (DEMO) to integrate an inner first wall constructed from low activation martensitic steel (e.g. EUROFER) that presents the drawback of being highly transparent to hydrogen isotopes. Moreover, the cooling system and other axes parts present high contamination risks and this imposes the use of permeation barriers to avoid a radioactive hazard. In this R&D context, we studied several oxides and metals known in the literature for their suitable permeation barrier properties. Therefore, single and co-deposited layers consisting of bulk metals (W, Be) and oxides (Al2O3, Cr2O3) were deposited utilizing RF Magnetron Sputtering @ Ar pressure and Thermionic Vacuum Arc (TVA) methods. Following the deposition process, we conducted a microstructural and microchemical evaluation, taking into consideration that different deposition conditions could influence the microstructure, morphology, and layer surfaces. Here we demonstrated that metallic, oxides, and metallic-oxides films can be deposited with a wide range of morphologies utilizing RF sputtering and TVA, as revealed by SEM measurements. Film morphologies were observed from compact (Cr2O3-Be, Al2O3, Al2O3-Be, Al2O3-W) to the homogenous distribution of particles in a dense matrix (W, Be-W, Cr2O3-W) and flakes (Be, Cr2O3). The chemical compositions were analyzed qualitatively using an energy-dispersive X-ray microanalysis (EDX) system. The EDX measurements indicate that the sputtered oxides (Al2O3, Cr2O3) contain O (at. %) at close values to the atomic ratio in stoichiometric configuration, confirming the coexistence of metal-oxide in a bulk state. The mechanical properties were evaluated by hardness, elastic modulus, and adhesion strength measurements using nano indenter and nano / micro scratch tester. Lower elastic modulus on metal-oxide co-depositions was observed while indentation hardness increased for Be and decreased for W matrix configurations. A significantly better adhesion behavior was observed for pure configurations of oxides (micro scratch) and metals (nano scratch), while co-depositions were highly sensitive to premature delamination. Additionally, we address investigations regarding the desorption of native trapped hydrogen utilizing thermal desorption spectrometry (TDS) instrument and also the bounding state of atoms at the surface of the metal-oxides configurations using X-ray photoelectron spectroscopy (XPS). Overall, a mixture of oxidized and metallic states of the constituent elements was observed in the near-surface layer. However, the Al0 unoxidized feature vanishes only for Al2O3-W configuration. The determined results will assist further optimizations of the deposition techniques to achieve dense and defect-free permeation barrier structures measurable to future laborious permeation investigations. Acknowledgment: This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS / CCCDI ? UEFISCDI, with the project number PD 192 ? 2020, within PNCDI III;

Authors : J. M. Duran-Pinilla*, A. C. Garcia-Castro*.
Affiliations : *School of Physics, Universidad Industrial de Santander, Calle 09 Carrera 27, Bucaramanga, Colombia.

Resume : The antiperovskite structure exhibits a diverse ensemble of unconventional physical and chemical properties generated by the wide structural features inherited from their perovskites counterparts and the allowed cations at X sites. As such, the Mn3AN family [1] has shown remarkable properties that go from piezomagnetic effect to frustrated magnetism making this field of broad interest within the scientific community. Among this type of materials, the Vanadium-based antiperovskite family, V3AN, has been also reported with A = Ga, Ge, As, and P in which, for A = P and As, superconducting properties were found [2]. Nevertheless, the V3AN previously studied has been reported to crystallize in a layered orthorhombic anti-postperovskite structure with space group Cmcm [3] far from the cubic symmetry shown by its Mn-based counterparts. Moreover, previous research has been mostly focused on experimental findings, such as sample synthesis and characterization of the superconducting mechanism exhibited in the anti-postperovskite phase. Then, similar cubic antiperovskite compounds among this family, where topological properties associated with intertwined magnetic structure and their symmetry, are still in pursuit. As such, in this study, we theoretically explored the structural stability and the chiral magnetism of a predicted Vanadium-based antiperovskite compound stable in the Pm3m cubic symmetry. Therefore, first-principles calculations in the framework of Density-functional theory, DFT, were carried out and were focused on the study of the structural, magnetic, and vibrational properties of a newly proposed V3AN compound. We demonstrate that the ground state structure belongs to a cubic phase and showed the structural stability of the material in this phase in terms of the phonon spectra. Furthermore, we found that the magnetic structure of the ground state symmetry shows a chiral magnetic ordering within a non-collinear antiferromagnetic state. The latter explained in terms of the magnetic frustration of the Vanadium atoms organized in a Kagomé lattice in the (111) planes. Finally, this symmetry and magnetic ordering make of this compound an ideal candidate for exploring enhanced topological properties such as Anomalous Hall conductivity. [1] Zemen, J., Mendive-Tapia, E., Gercsi, Z., Banerjee, R., Staunton, J. B., & Sandeman, K. G. (2017). Frustrated magnetism and caloric effects in Mn-based antiperovskite nitrides: Ab initio theory. Physical Review B, 95(18), 184438. [2] Wang, B., & Ohgushi, K. (2013). Superconductivity in anti-post-perovskite vanadium compounds. Scientific reports, 3(1), 1-5. [3] Wang, B. S., Cheng, J. G., Matsubayashi, K., Uwatoko, Y., and Ohgushi, K. (2014). High-pressure effects in anti-post-perovskite superconductors V3PnN x (Pn= P, As), Physical Review B, 89(14), 144510.

Authors : Sunju Kang, Sunkook Kim
Affiliations : Sungkyunkwan University

Resume : Wearable epidermal sensor systems have gained tremendous attention for real-time healthcare monitoring devices with different sensor geometry and device architectures. In this work, a stretchable-gradient structure is introduced to the nature-inspired kirigami-serpentine based temperature sensor with an integration of flexible printed circuit board (FPCB) and stretchable interconnection to obtain real-time monitoring of body temperature with high accuracy and sustainability under complex mechanical conditions. The electrical and mechanical properties are measured with multiple testing processes and the results show a linear response under different temperature ranges and high robustness properties over multiple strain tests. A three-layer wearable patch is designed to establish a conformable bonding to human skin and obtain wireless real-time monitoring of body temperature, thus, establishing a new approach towards real-time healthcare monitoring devices with high accuracy and stability over complex environments in the field of wearable electronics.

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New Materials 2 : tba
Authors : Jun Zhou1, Jingyang You1, L. Shen2, Y. P. Feng1,3
Affiliations : 1Department of Physics, National University of Singapore, Singapore, 117551 2Department of Mechanical Engineering, National University of Singapore, Singapore, 117575 3Centre for Advanced Two-Dimensional Materials, National University of Singapore, Singapore, 117546

Resume : Two-dimensional (2D) materials have attracted a lot of interest. Their unique properties are expected to lead to new technologies. In an effort of systematic 2D materials discovery, we have been using both the top-down and the bottom-up approaches to generate 2D structures. On one hand, monolayer structures are theoretically exfoliated from layered three-dimensional structures by a topology-based algorithm. On the other hand, new 2D materials are systematically generated by chemical substitution of elements in the top-down 2D compounds by similar elements. High throughput first-principles calculations are carried out to study their physical properties. The 2D materials database, 2DMatPedia1, is publicly available and provides a good starting point for further material screening, data mining, data analysis and artificial intelligence applications2. In this talk, I will provide an update on the development and the current status of the 2D materials genome, and discuss some examples of materials discovery based on the database. By screening through 2D materials in 2DmatPedia, intrinsic ferromagnetism was discovered in several monolayer electrides or electrenes such as lanthanum bromide, in which excess electrons act as anions. The origin of magnetism and magnetic coupling in such electrenes are totally different from that in conventional magnetic materials. The electrenes were found to process relatively high Curie temperature and coercivity, suggesting potential applications in spintronic devices. In another example, a 2D tungsten nitride, which can be exfoliated from the bulk material with a low exfoliation energy, was found to be a topological metal with exotic topological states at different energy levels. Moreover, monolayer W2N3 is found to be a superconductor with the superconducting transition temperature of ∼ 22 K and a superconducting gap of about 5 meV. References: 1. 2. Jun Zhou et al., 2DMatPedia, an open computational database of two-dimensional materials from top-down and bottom-up approaches, Scientific Data 6, 86 (2019) 3. Jun Zhou et al., Atomic-orbital-free intrinsic ferromagnetism in electrenes, Phys. Rev. B 102, 180407(R) (2020). 4. Jingyang You et al., Two-dimensional topological superconductivity candidate in a van der Waals layered material, Phys. Rev. B 103, 104503 (2021).

Authors : John S. Tse and Jacques K. Desmarais
Affiliations : Department of Physics and Engineering Physics University of Saskatchewan Saskatoon, Canada

Resume : Strongly correlated materials are characterized by partially occupied d and/or f-type bands with highly localized unpaired electrons. Under compression, the hybridization of these bands causes competing valence states, and resulted in so-called mixed valency. The prototypical example is EuO. Under compression, EuO exhibits several structural transitions. It has been suggested the transformations are associated in the change in the Eu oxidation state from +2 to +3 [1.2]. We show that the isostructural transitions can be reproduced by the standard KS-DFT approach with a self-interaction correction included in the global-hybrid functional with all-electron basis sets [3]. The pressure-dependent change in the x-ray absorption spectra [2] is related to changes in the electron density of the unoccupied d-band in the different crystal fields. There is no need to invoke mixed valency to account for the experimental observations. Another example on the importance of using explicit all-electron basis sets is illustrated in the electronic structure calculations in pressure-induced changes in the 57Fe Mossbauer chemical shift of pure Fe and Fe oxides [4]. It is found that good numerical agreements with experimental measurements can be achieved with the B1WC hybrid functional. Analysis of the electronic structure shows a substantial donation of electrons from oxygen to iron at high pressure. The assignment of formal oxidation to the Fe atom becomes ambiguous under this condition. References 1. A. Jayaraman, Phys. Rev. Lett. 29, 1674 (1972) 2. N. M. Souza-Neto,, Phys. Rev. Lett. 109, 026403 (2012). 3. J.K. Desmarais,, Phys. Rev. Lett., 126, 196404 (2021) 4. J.K. Desmarais., J. Chem. Phys. 154, 214104 (2021).

Authors : Xiancheng Wang, Jun Zhang, Changqing Jin
Affiliations : Institute of Physics, Chinese Academy of Sciences, Beijing, China

Resume : Here, we report a series of new materials A3BX5 with quasi one-dimensional (1D) chains synthesized at the conditions of high pressure and high temperature, where A denotes Ba or La, B is 3d transition metal and X represents chalcogen or pnicogen element [1-6]. These compounds consist of face-sharing BX6 octahedral chains running in c-direction and these chains are separated with a distance >9 Å, showing a strong 1D structural character. In these quasi 1D system, it is demonstrated that when the anion of X changes from low periodic element to high periodic one their resistivity will decrease and the long range order temperature will be enhanced because of the increase of interchain electron hopping. References: [1]. Zhang, J., Wang, X.C., Jin, C.Q., et al. "High-pressure synthesis, crystal structure, and properties of iron-based spin-chain compound Ba9Fe3Se15". Phys. Rev. Mater. 5, 054606 (2021). [2]. Zhang, J., Wang, X.C., Jin, C.Q., et al. "A New Quasi One-Dimensional Compound Ba3TiTe5 and Superconductivity Induced by Pressure". NPG Asia Materials 11, 60 (2019). [3]. Zhang, J., Wang, X.C., Jin, C.Q., et al. "The synthesis of a quasi-one-dimensional iron-based Telluride with antiferromagnetic chains and a spin glass state". Inorg. Chem. 59, 5377 (2020). [4]. Zhang, J., Wang, X.C., Jin, C.Q., et al. "Ba9V3Se15: a novel compound with spin chains". J. Phys.: Condens. Matter 30, 214001 (2018). [5]. Duan, L., Wang, X.C., Jin, C.Q., et al. "High-pressure synthesis, crystal structure and physical properties of a new Cr-based arsenide La3CrAs5". Science China Materials 63, 1750 (2020). [6]. Duan, L., Wang, X.C., Jin, C.Q.,et al. "High-pressure synthesis, structure and properties of new ternary pnictides La3TiX5 (X = P, As)". Journal of Alloys and Compounds 831, 154697 (2020). [7]. Zhang, J., Wang, X.C., Jin, C.Q.,et al. "Synthesis, crystal structures, and electronic properties of one dimensional Ba9Sn3(Te1-xSex)15 (x = 0-1)", Inorganic Chemistry Frontiers 4, 1337 (2017)

Authors : Juan Manuel Bermudez-Garcia, Jorge Salgado-Beceiro, Javier García-Ben, Ignacio Delgado-Ferreiro, Manuel Sanchez-Andujar, Socorro Castro-Garcia and Maria Antonia Señaris-Rodriguez
Affiliations : University of A Coruna, QuiMolMat Group, Dpt. Chemistry, Faculty of Science and Advanced Scientific Research Center (CICA), Zapateira, 15071 A Coruña, Spain.

Resume : Hybrid organic-inorganic compounds are an emerging family of materials that integrates organic and inorganic building blocks in their chemical structures.[1] In the recent years, these materials have exhibited several functional properties of great interest for energy applications, such as remarkable photovoltaic and optoelectronic properties for low-cost solar cells, in the case of lead halide-perovskites,[2] or enormous gas absorption capacities for hydrogen storage or CO2 capture, in the case of metal-organic frameworks (MOFs).[3] Even more recently, our research group have pioneered studies on hybrid organic-inorganic as new materials for solid-state cooling, heating and multiple energy storage.[4] Therefore, these solid compounds arise as a new alternative to the current refrigerant gases, which are mainly toxic, flammable and/or greenhouse gases. In this work, we present our more recent advances in the design and study of new hybrid materials (hybrid perovskites and ionic plastic crystals) that exhibit multiple phase transitions, which are sensible towards multiple external stimuli (such as pressure, temperature, and/or electric field).[4] These phase transitions are associated with very large thermal changes, which can occur simultaneously with large changes in their dielectric capacity. In turn, these remarkable functional properties are very promising, not only for solid-state cooling/heating, but also for multiple energy (thermal and electric) storage. Additionally, we analyse the relationships between the aforementioned properties and the structure features of these materials (such as configurational disordering, distortions, chemical modulation, among others), which will help to design future compounds with enhanced multifunctional properties of interest for eco-friendly refrigeration and heating applications. In summary, we introduce a new family of multifunctional hybrid organic-inorganic compounds whose large sensibility towards different external stimuli (pressure, temperature and/or electric fields) makes them as promising candidates for solid-state and gas-free cooling/heating technologies. References: [1] (a) O. M. Yaghi et al., Nature, 2003, 423, 705-714; (b) A. K. Cheetham and C.N.R. Rao, Science, 2007, 318, 58-59. [2] (a) M.M. Lee et al., Science, 2021, 338, 643-647; (b) J. Burschka et al., Nature, 2013, 499, 316-319. [3] (a) M. Ding et al., Chem. Soc. Rev. 2019, 48, 2783-2828; (b) M. T. Kapelewski et al., Chem. Mater., 2018, 30, 8179-8189. [4] (a) J. M. Bermúdez-García et al., Nat. Commun., 2017, 8, 15715; (b) J. M. Bermúdez-García et al., J. Phys. Chem. Lett., 2017, 8, 4419; (c) J. M. Bermúdez-García et al., J. Mater. Chem. C, 2018, 6, 9867; (d) J. Salgado-Beceiro et al., Mater. Adv., 2020, 1, 3167; (e) J. Salgado-Beceiro et al., J. Mater. Chem. C, 2020, 8, 13686-13694.

15:45 Q&A Session / Break    
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Special Materials 1 : tba
Authors : Guozhong Zhao
Affiliations : Department of Physics, Capital Normal University, Beijing 100048, China

Resume : Terahertz functional components such as polarizers, modulators and filters, are crucial devices for different terahertz applications. The functional materials are the basic of functional devices. The terahertz functional materials based on the metasurfaces are paid more and more attentions in recent year due to the lack of national materials in the terahertz frequency regions. The terahertz functional materials based on the structures of metallic array are firstly studied in this work. The planar metallic structures consist of periodic array with the different unit cell of structures. The optimized design of structure parameters of metallic arrays is simulated and discussed. The spectral characteristic of metallic array structures is investigated by the terahertz time-domain spectroscopy. The terahertz modulation functionality of these metallic structures is presented and discussed. In detail, the one-dimensional metallic wire grating as a potential terahertz polarizer is designed and fabricated. The terahertz time-domain spectroscopy is used to measure the transmission of metallic grating. Moreover, two-dimensional metallic slit array as a potential terahertz attenuator is designed and analyzed. The polarization dependence of metallic slit array is discussed. The metallic cross array as a potential terahertz filter is analyzed. Finally, the terahertz vortex phase plates, which can generate the terahertz vortex beams, are designed and simulated numerically. The terahertz metasurfaces with the order structures of different functional elements are demonstrated that can provide the various functionalities for the modulation of terahertz wave. The research on the terahertz metasurfaces is helpful for the development of terahertz functional devices.

Authors : Takami Tohyama
Affiliations : Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan

Resume : Electric pulse applied to materials changes states of matter and induces novel states. These changes may come from modification of microscopic interactions, crystalline structural, carrier density, and so on. Such photo-induced phenomena are one of current topics in strongly correlated electron systems. Mott insulating states are a good play ground for the phenomena. We firstly focus on a two-dimensional Mott insulator with square lattice, which is a parent compound of cuprate high temperature superconductors. Calculating momentum-dependent spin dynamics induced by pumping electric pulse numerically, we find an antiphase oscillation of spectral weight in the spin structure factor between momentum q=(,0) and (0,), which can be detectable by time-resolved resonant inelastic x-ray scattering [1]. The oscillation is partly originated from antiferromagnetic exchange interaction modified by the pumping pulse. We next examine photo-doping effect on a one-dimensional Mott insulator by calculating time-resolved optical conductivity numerically [2]. We find the appearance of photocarriers in the optical conductivity strongly depends on the frequency of the pumping pulse. [1] K. Tsutsui, K. Shinjo, and T. Tohyama, Phys. Rev. Lett. 126, 127404 (2021). [2] K. Shinjo, S. Sota, and T. Tohyama, in preparation.

Authors : Antoine Bodin, Thomas Pietri, Jean-Pierre Simonato
Affiliations : Université Grenoble Alpes, CEA, LITEN, DTNM, 38000 Grenoble, France

Resume : With the intensifying development of electronics and energy storage systems (e.g. batteries for electrical vehicles) where a lot of heat is generated in operation, new high-performance heat dissipative materials need to be developed. Their goal is to help the heat dissipation in order to avoid overheating, hotspots or thermal runaways that could damage integrated circuits or threaten safety. In this study, nanocomposites made of polycarbonate (PC) and boron nitride nanotubes (BNNTs) as nanofillers are investigated (PC-BNNT systems). Boron nitride nanotubes are one of the most promising inorganic nanomaterials used to improve thermal conductivity while preserving the electrical insulation of the nanocomposites. This study focuses on incorporation of raw boron nitride nanotubes inside a polymer matrix made of polycarbonate via solution mixing. The thermal conductivity of this PC-BNNT system reaches 0.83 W/mK at 30wt% of raw BNNTs (which is approximatively 280% higher than neat PC). In addition to the thermal measurements, dispersibility of the nanotubes and their chemical affinity with the polycarbonate matrix are investigated through a SEM-EDX analysis.

10:00 Q&A Session / Break    
Special Materials 2 : tba
Authors : Z. Guguchia1, D. Das1, C.N. Wang1, T. Adachi2, N. Kitajima3, M. Elender1, F. Brückner4, S. Ghosh4, V. Grinenko4,5, T. Shiroka1,6, M. Müller7, C. Mudry7,8, C. Baines1, M. Bartkowiak9, Y. Koike3, A. Amato1, J. M. Tranquada10, H.-H. Klauss4, C.W. Hicks11, H. Luetkens1
Affiliations : 1Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 2Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan 3Department of Applied Physics, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan 4Institute for Solid State and Materials Physics, Technische Universitat Dresden, D-01069 Dresden, Germany 5Leibniz-Institut fur Festkorper- und Werkstoffforschung (IFW) Dresden, 01171 Dresden, Germany 6Laboratorium fur Festkorperphysik, ETH Zurich, CH-8093 Z¨urich, Switzerland 7Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 8Institute of Physics, Ecole Polytechnique Fedeerale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland 9Laboratory for Scientific Developments and Novel Materials, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland 10Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY 11973, USA 11Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany

Resume : Cuprate high-temperature superconductors (HTSs) have complex phase diagrams with multiple competing ordered phases. Understanding to which degree charge, spin, and superconducting orders compete or coexist is paramount for elucidating the microscopic pairing mechanism in the cuprate HTSs. In this talk, I will report some novel results of muonspin rotation (μSR) and AC susceptibility experiments on uniaxial stress effect on the static spin-stripe order and superconductivity in the La214 cuprates [1]. We find that in the cuprate system La2-xBaxCuO4 with x = 0.115, an extremely low uniaxial stress of 0.05 GPa induces a substantial decrease in the magnetic volume fraction and a dramatic rise in the onset of 3D superconductivity, from 10 to 32 K; however, the onset of at-least-2D superconductivity is much less sensitive to stress [1]. These results show not only that large-volume-fraction spin-stripe order is anti-correlated with 3D superconducting (SC) coherence, but also that these states are energetically very finely balanced. Moreover, the onset temperatures of 3D superconductivity and spin-stripe order are very similar in the large stress regime. These results strongly suggest a similar pairing mechanism for spin-stripe order, the spatially-modulated 2D and uniform 3D SC orders, imposing an important constraint on theoretical models. [1] Z. Guguchia et. al., Phys. Rev. Lett. 125, 097005 (2020).

Authors : Maarit Karppinen
Affiliations : Department of Chemistry and Materials Science, Aalto University, Finland

Resume : The rarest of the trivalent iron oxide polymorphs, i.e. ferrimagnetic ε-Fe2O3, could open new horizons for high-density magnetic storage, owing to its giant coercive field (⁓20 kOe at RT). It is moreover non-toxic, biocompatible and composed of non-critical elements, but the difficulty lies in its limited stability and challenging synthesis, in particular beyond the trace amounts enabled through conventional synthesis techniques. We have successfully developed a facile gas-phase synthesis route for amazingly stable ε-Fe2O3 thin films based on atomic layer deposition (ALD),[1] the fastest growing thin-film technology in microelectronic industry. An emerging trend in the field is to combine with ALD additional molecular layer deposition (MLD) cycles for organic layers. We have utilized the combined ALD/MLD approach to introduce with digital accuracy monomolecular benzene or azobenzene layers[2] within the ε-Fe2O3 matrix. These organic layers significantly improve the mechanical properties of the ε-Fe2O3 films without compromising their unique magnetic properties.[3] Most excitingly, the azobenzene moieties are photoresponsive, undergoing upon UV irradiation a reversible trans-cis isomerization accompanied with a considerable dimensional change, i.e. a kind of chemical pressure effect on the ε-Fe2O3 layers. Very recently we demonstrated for the azobenzene embedded ε-Fe2O3 films reversible changes in both coercivity and magnetization values with alternating irradiations of the films with UV and visible light.[4] We believe that these results are a step ahead towards the dream of switchable on-and-off type flexible hard magnets operating at room temperature. 1. Tanskanen, O. Mustonen & M. Karppinen, Simple ALD process for ε-Fe2O3 thin films, APL Mater. 5, 056104 (2017). 2. A. Khayyami, A. Philip & M. Karppinen, Atomic/molecular layer deposited iron-azobenzene framework thin films for stimuli-induced gas molecule capture/release, Angew. Chem. 58, 13400 (2019). 3. A. Philip, J.-P. Niemelä, G.C. Tewari, B. Putz, T.E.J. Edwards, M. Itoh, I. Utke & M. Karppinen, Flexible ε-Fe2O3-terephthalate thin-film magnets through ALD/MLD, ACS Appl. Mater. Interfaces 12, 21912 (2020). 4. A. Philip, Y. Zhou, G.C. Tewari, S. van Dijken & M. Karppinen, Optically controlled large-coercivity room-temperature thin-film magnets, in preparation (2021).

Authors : Manuel Angst
Affiliations : Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

Resume : Magnetite is not only the oldest known magnetic material, but also the classical (1939) example of a metal-insulator transition, at TVerwey=120 K [1]. This transition has been attributed to charge (iron valence) ordering, which might be ferroelectric as proposed in several reports based on electric characterization [2]. Dielectric spectroscopy indicates relaxor ferroelectric characteristics, with polarization switching observable only at low T and in a suitably chosen time-window [3]. The very complex low T crystal structure had been only solved recently, and found to be polar [4]. Intrinsic ferroelectricity additionally requires that this polar structure can be switched by an applied electric field. Given the relaxor characteristics, structural switching can only be observable in the proper time-window. I will present a time-resolved x-ray diffraction study on single crystalline magnetite with electric field pulses applied in-situ that indicates that structural switching does occur for sufficiently large electric fields [5]. [1] E.J.W. Verwey, Nature 144, 327 (1939). [2] e.g. G.T. Rado et al., Phys. Rev. B 12, 5166 (1975); K.Kato et al., J. Magn. Magn. Mater. 31-34, 783 (1983); Y. Miyamoto et al., Ferroelectrics 93, 301 (1989); M. Alexe et al., Adv. Mater. 21, 4452 (2009). [3] F. Schrettle, S. Krohns, P. Lunkenheimer, V.A.M. Brabers, and A. Loidl, Phys. Rev. B 83, 195109 (2011). [4] M.S. Senn, J.P. Wright, and J.P. Attfield, Nature 481, 173 (2012). [5] M. Angst, S. Adiga, S.Gorfman, M. Ziolkowski, J. Strempfer, C. Grams, M. Pietsch, and J. Hemberger, Crystals 9, 546 (2019).

Authors : K. Zhao*(1, 2), T. Hajiri (3), H. Chen (4), R. Miki (3), H. Asano (3) & P. Gegenwart (1).
Affiliations : (1) Experimentalphysik VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany (2) School of Physics, Beihang University, Beijing 100191, China (3) Department of Materials Physics, Nagoya University, Nagoya 464-8603, Japan (4) Department of Physics, Colorado State University, Fort Collins, CO 80523-1875, USA

Resume : The anomalous Hall effect (AHE) in conventional ferromagnetic metals is proportional to the net magnetization and was expected to vanish in antiferromagnets. However, it is now well understood that the existence of the AHE is constrained by symmetry and is not necessarily incompatible with AFM order. This principle has been exemplified by the large AHE predicted and realized in various noncollinear AFMs, such as hexagonal Mn3Sn/Ge and cubic Mn3Ir/Pt, etc. where the Mn atoms form a kagome lattice along different crystalline planes. In these materials, geometric frustration and local symmetries of the magnetic atoms to gather lead to a chiral noncollinear magnetic order with the essential symmetry breaking for finite AHE, which is also reflected by the small net moment in certain crystalline directions. The large AHE in the hexagonal Mn3Sn/Ge was argued to be due to Weyl points near the Fermi energy. Technologically, the robust AHE at room temperature in these systems makes them attractive for potential applications in spintronics solely based on AFM. Meanwhile, it is interesting to search for similar anomalous Hall antiferromagnets (AHE AFMs) beyond binary Mn compounds, which may have other superior properties. Anti-perovskite manganese nitrides Mn3AN, have received a lot of attention due to a number of unusual physical properties, such as giant negative thermal expansion, temperature independent resistivity, and barocaloric effects. All of these phenomena are closely related to the first order phase transition from a high temperature paramagnetic cubic phase into a low temperature noncollinear AFM phase with the so-called Γ4g and Γ5g magnetic structures. It is interesting to notice that the Mn atoms form a 1/4-depleted fcc lattice in these manganese antiperovskites, whose (111) planes are kagome lattices. Therefore one would expect there to be AHE if the AFM order of the Mn moments is similar to these binary compounds. We report the topological AHE in antiperovskite Mn3NiN with substantial doping of Cu on the Ni site (i.e. Mn3Ni1−xCuxN), which stabilizes a noncollinear antiferromagnetic (AFM) order compatible with the AHE. Observed on both sintered polycrystalline pieces and single crystalline films, the AHE does not scale with the net magnetization, contrary to the conventional ferromagnetic case. The existence of the AHE is explained through symmetry analysis based on the Γ4g AFM order in Cu doped Mn3NiN. DFT calculations of the intrinsic contribution to the AHE reveal the non-vanishing Berry curvature in momentum space due to the noncollinear magnetic order. The binary Mn compounds encounter potential non-wetting and interfacial oxidation problems during the epitaxial thin-film growth on oxide substrates. Thus, it is much easier to obtain high quality epitaxial Mn3Ni1−xCuxN film on oxide substrates, giving much advantage for the preparation of multilayer devices in AFM spintronics. Reference: K. Zhao et al., PRB 100, 045109 (2019)

12:45 Q&A session / Closing Remarks    

Symposium organizers
Changqing JINInstitute of Physics, Chinese Academy of Sciences

Beijing 100190, China
Roman PUZNIAKInstitute of Physics, Polish Academy of Sciences

Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
Shinichi UCHIDAUniversity of Tokyo

Wada 1-4-5-501, Suginami-ku, Tokyo 166-0012, Japan