Pressure tuning the lattice and optical response of silver sulfide

TL;DR

This study demonstrates how applying high pressure to silver sulfide induces structural phase transitions and transforms its electronic properties from semiconducting to metallic, revealing pressure as a powerful tuning tool.

Contribution

It provides a systematic in situ analysis of Ag2S's structural and optical changes under pressure, highlighting pressure-induced phase transitions and electronic evolution.

Findings

Ag2S undergoes monoclinic to orthorhombic transition under pressure.

Pressure induces a transition from semiconductor to metal at ~22 GPa.

Optical conductivity peaks at ~40 GPa, indicating maximum metallic behavior.

Abstract

Binary transition metal chalcogenides have attracted increasing attention for their unique structural and electronic properties. High pressure is powerful tool for tuning their crystal structure and electronic structure away from their pristine states.In this work, we systematically studied the in situ structural and optical behavior of silver sulfide (Ag2S) under pressure by X-ray diffraction (XRD) and Infrared (IR) spectroscopy measurements in a diamond anvil cell. Upon compression, Ag2S undergoes structural symmetrization from monoclinic to orthorhombic, represented by the decrease of angle from 99 to 90 degrees through a series of structural transitions coupled with lattice contractions. IR transmission and reflectivity measurements showed that pressure effectively tunes semiconducting Ag2S into a metal at ~ 22 GPa. Drude model analysis of the IR reflectivity indicates that the optical conductivity evolves significantly, reaching the highest conductivity at ~ 40 GPa. Our results highlight pressure's dramatic role in tuning the structural and electronic state of silver chacogenides.