Atomic and electronic structures evolution of the narrow band gap semiconductor Ag sub(2)Se under high pressure

Non-trivial electronic properties of silver telluride and other chalcogenides, such as the presence of a topological insulator state, electronic topological transitions, metallization, and the possible emergence of superconductivity under pressure have attracted attention in recent years. In this wo...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2016-09, Vol.28 (38), p.385801-385806
Main Authors: Naumov, P, Barkalov, O, Mirhosseini, H, Felser, C, Medvedev, S A
Format: Article
Language:English
Subjects:
Electrical resistivity
Electronic structure
Insulators
Mathematical analysis
Semiconductors
Silver
Temperature dependence
Topology
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Summary:Non-trivial electronic properties of silver telluride and other chalcogenides, such as the presence of a topological insulator state, electronic topological transitions, metallization, and the possible emergence of superconductivity under pressure have attracted attention in recent years. In this work, we studied the electronic properties of silver selenide (Ag sub(2)Se). We performed direct current electrical resistivity measurements, in situ Raman spectroscopy, and synchrotron x-ray diffraction accompanied by ab initio calculations to explore pressure-induced changes to the atomic and electronic structure of Ag sub(2)Se. The temperature dependence of the electrical resistivity was measured up to 30 GPa in the 4-300 K temperature interval. Resistivity data showed an unusual increase in the thermal energy gap of phase I, which is a semiconductor under ambient conditions. Recently, a similar effect was reported for the 3D topological insulator Bi sub(2)Se sub(3). Raman spectroscopy studies revealed lattice instability in phase I indicated by the softening of observed vibrational modes with pressure. Our hybrid functional band structure calculations predicted that phase I of Ag sub(2)Se would be a narrow band gap semiconductor, in accordance with experimental results. At a pressure of ~7.5 GPa, Ag sub(2)Se underwent a structural transition to phase II with an orthorhombic Pnma structure. The temperature dependence of the resistivity of Ag sub(2)Se phase II demonstrated its metallic character. Ag sub(2)Se phase III, which is stable above 16.5 GPa, is also metallic according to the resistivity data. No indication of the superconducting transition is found above 4 K in the studied pressure range.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/28/38/385801