Kavli Affiliate: Cheng Peng
| First 5 Authors: Juyeon Won, Rong Zhang, Cheng Peng, Ravhi Kumar, Mebatsion S. Gebre
| Summary:
Recent band structure calculations have suggested the potential for band
tuning in a chiral semi-conductor, 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% of the lattice constant resulted
in a pressure-induced structural transformation, indicating the potential for
substantial gap modulation under extreme compression conditions.
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