High-pressure characterization of Ag$_3$AuTe$_2$: Implications for strain-induced band tuning

TL;DR

This study synthesizes Ag$_3$AuTe$_2$, investigates its properties under pressure, and confirms that high compression can induce structural changes that support strain-induced band gap tuning as predicted by theoretical calculations.

Contribution

It provides experimental validation of pressure-induced structural transformations in Ag$_3$AuTe$_2$ supporting its potential for strain-tunable electronic properties.

Findings

Ag$_3$AuTe$_2$ exhibits semiconducting behavior with high resistivity.

Optical and transport measurements show a band gap consistent with DFT predictions.

High-pressure experiments reveal structural transformations beyond 4% compression.

Abstract

Recent band structure calculations have suggested the potential for band tuning in a chiral semiconductor, Ag$_3$AuTe$_2$, to zero upon application of negative strain. In this study, we report on the synthesis of polycrystalline Ag$_3$AuTe$_2$ and investigate its transport, optical properties, and pressure compatibility. Transport measurements reveal the semiconducting behavior of Ag$_3$AuTe$_2$ with high resistivity and an activation energy $E_a$ of 0.2 eV. The optical band gap determined by diffuse reflectance measurements is about three times wider than the experimental $E_a$. Despite the difference, both experimental gaps fall within the range of predicted band gaps by our first-principles DFT calculations employing the PBE and mBJ methods. Furthermore, our DFT simulations predict a progressive narrowing of the band gap under compressive strain, with a full closure expected at a strain of -4% relative to the lattice parameter. To evaluate the feasibility of gap tunability at such substantial strain, the high-pressure behavior of Ag$_3$AuTe$_2$ was investigated by $in$ $situ$ high-pressure X-ray diffraction up to 47 GPa. Mechanical compression beyond 4% resulted in a pressure-induced structural transformation, indicating the possibilities of substantial gap modulation under extreme compression conditions.