Quantum Matter Institute (University of British Columbia, Canada)

报告摘要：

Entropy in materials can play a role in stabilizing phases above a critical entropy threshold and enhancing material properties through configurational disorder [1,2]. Typically, the focus has been on the contribution of atomic species to the total entropy. Here, we extend this framework by introducing the concept of charge-entropy stabilization in the rocksalt superconductor (Ag,Sn)Se. We expect Sn to exist in a mixed-valent state, fluctuating between Sn²⁺/Sn⁴⁺, for the experimentally realized compositions [3]. We present spectroscopic evidence from HEXPES and Mössbauer measurements confirming the persistence of charge fluctuations down to 4 K, below the superconducting transition temperature [4]. We develop a model based on the mixed valence of Sn, considering the ionic species Ag¹⁺/Sn²⁺/Sn⁴⁺, that captures the observed phase stability region. This proposed model may allow for the synthesis of other superconducting rocksalt compounds containing valence-skipping elements.

Reference:

[1] S. Schweidler, et al., Nat. Rev. Mater. 9: 266-281 (2024).

[2] S. S. Aamlid, M. Oudah, et al., JACS 145.11: 5991-6006 (2023).

[3] A. Wold, and R. Brec.,  Mater. Res. Bull. 11, 761 (1976).

[4] M. Oudah, et al., Commun. Mater. 6.1: 58 (2025).

报告人简介：

Mohamed Oudah is a Research Associate at the Quantum Matter Institute (QMI), University of British Columbia, Canada, where he works on the synthesis and discovery of novel quantum materials, including high-entropy oxides and correlated systems. Dr. Oudah earned his Ph.D. in Physics from Kyoto University for his work on superconductivity in antiperovskite oxides. He also holds an M.Sc. in Chemistry–Nanotechnology from the University of Waterloo and a B.Eng. in Chemical Engineering from the University of Ottawa. His research background includes positions at Princeton University, the Max Planck Institute for Solid State Research in Stuttgart, and Kyoto University. He has received the MEXT Research Scholarship. He has more than 30 publications, including NM, PRX, NC etc.

邀请人：李西阳 副研究员

联系人：王慧颖 why@iphy.ac.cn

报告地点：怀柔园区X1南楼101会议室

腾讯会议：679-889-743

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