We performed synchrotron x-ray diffraction and infrared (IR) experiments combined with evolutionary structure predictions and band structure calculations on Ag2Se to ∼20 GPa. We present evidence for phase I (β-Ag2Se) as a potential three-dimensional topological insulator by its increase in optical band gap and the topologically nontrivial nature of its band structure. Higher pressures induce a triple-layer stacking pattern and significantly increase the crystallographic inequivalence of the two Ag sites, where P212121 phase I first reconstructs into a Pnma phase II, and then transforms into a topologically different Cmcm phase III. The radical changes in IR spectra and electronic band structures indicate the metallic nature of the high-pressure phases. Our results highlight the effects of pressure in tuning the crystal structure and electronic states of Ag2Se.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 22 May 2014|