High-pressure characterization of Ag₃AuTe₂: Implications for strain-induced band tuning

Recent band structure calculations have suggested the potential for band tuning in the chiral semiconductor Ag₃AuTe₂ to zero upon application of negative strain. In this study, we report on the synthesis of polycrystalline Ag₃AuTe₂ and investigate its transport and optical properties and mechanical compressibility. Transport measurements reveal the semiconducting behavior of Ag₃AuTe₂ with high resistivity and an activation energy E a of 0.2 eV. The optical bandgap 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 bandgaps by our first-principles density functional theory (DFT) calculations employing the Perdew-Burke-Ernzerhof and modified Becke-Johnson methods. Furthermore, our DFT simulations predict a progressive narrowing of the bandgap 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 Ag₃AuTe₂ 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 possibility of substantial gap modulation under extreme compression conditions.