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

Recent band structure calculations have suggested the potential for band tuning in a chiral semi-conductor, Ag₃AuTe₂, to zero upon application of negative strain. In this study, we report on the synthesis of polycrystalline Ag₃AuTe₂ and investigate its transport, optical properties, and pressure compatibility. Transport measurements reveal the semiconducting behavior of Ag₃AuTe₂ with high resistivity and an activation energy Eₐ of 0.2 eV. The optical band gap determined by diffuse reflectance measurements is about three times wider than the experimental Eₐ. 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 Ag₃AuTe₂ was investigated by $in$ $situ$ high-pressure X-ray diffraction up to 47 GPa. Mechanical compression beyond 4% of the lattice constant resulted in a pressure-induced structural transformation, indicating the potential for substantial gap modulation under extreme compression conditions.