Isosymmetric phase transitions, ultrahigh ductility, and topological nodal lines in α- A g2 S

Yongcheng Liang*, Azkar Saeed Ahmad, Jianzhou Zhao, Guozhu Song, Xuefeng Zhou, Jialin Ji, Wei Zhang, Zhilin Han, Jixuan Liu, Kenny Ståhl, Anna Pakhomova, Konstantin Glazyrin, Guo Jun Zhang, Wenqing Zhang, Yusheng Zhao, Rui Yu, Shanmin Wang, Peihong Zhang

*Corresponding author for this work

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We report two reversible pressure-induced isosymmetric phase transitions in α-Ag2S that are accompanied by two compressive anomalies at 7.5 and 16 GPa, respectively. The first transition arises from a sudden and drastic puckering of the wrinkled Ag-S layers, which leads to an anomalous structural softening at high pressure and gives rise to the ultrahigh compressive ductility in α-Ag2S. The second transition stems from a pressure-driven electronic state crossover from a conventional semiconductor to a topological metal. The band-crossing points near the Fermi energy form a nodal-line structure due to the preservation of the time-reversal and space-inversion symmetries under pressure. Our findings not only reveal the underlying mechanism responsible for the ultrahigh ductility in this class of inorganic semiconductors, but also provide a distinctive member to the growing family of topological metals and semimetals.

Original languageEnglish
Article number140101
JournalPhysical Review B
Issue number14
Publication statusPublished - 2020


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