Electronic Topological Transition in Ag(2)Te at High-pressure

Recently, Ag(2)Te was experimentally confirmed to be a 3D topological insulator (TI) at ambient pressure. However, the high-pressure behaviors and properties of Ag(2)Te were rarely reported. Here, a pressure-induced electronic topological transition (ETT) is firstly found in Ag(2)Te at 1.8 GPa. Before ETT, the positive pressure coefficient of bulk band-gap, which is firstly found in TIs family, is found by both first-principle calculations and in situ high-pressure resistivity measurements. The electrical resistivity obtained at room temperature shows a maximum at 1.8 GPa, which is nearly 3.3 times to that at ambient pressure. This result indicates that the best bulk insulating character and topological nature in Ag(2)Te can be obtained at this pressure. Furthermore, the high-pressure structural behavior of Ag(2)Te has been investigated by in situ high-pressure synchrotron powder X-ray diffraction technique up to 33.0 GPa. The accurate pressure-induced phase transition sequence is firstly determined as P2(1)/c → Cmca → Pnma. It is worth noting that the reported isostructural P2(1)/c phase is not existed, and the reported structure of Cmca phase is corrected by CALYPSO methodology. The second high-pressure structure, a long puzzle to previous reports, is determined as Pnma phase. A pressure-induced metallization in Ag(2)Te is confirmed by the results of temperature-dependent resistivity measurements.