A DFT based first-principles investigation of optoelectronic and structural properties of Bi2Te2Se

Bi2Te2Se is a topological insulator (TI) having conducting surface electronic states with an energy gap in the bulk electronic band structure. Such systems are promising for variety of superconducting and quantum computation related applications. In addition, TIs may possess other important bulk physical characteristics appropriate for more conventional applications which are not affected significantly by spin-orbit interaction. In this study we focus on bulk properties of Bi2Te2Se which are not greatly affected by the surface electronic states and therefore, by spin-orbit coupling. We have investigated elastic, mechanical, electronic, optical properties, bonding character and the electronic charge density distribution of ternary Bi2Te2Se to explore its feasibility for potential applications. Bi2Te2Se is found to be mechanically stable and elastically anisotropic. Electronic effective mass is high in the c-direction compared to that in the ab-plane. The optical constants show moderate level of variation with respect to the polarization of the electric field of the incident radiation. The optical spectra are consistent with the bulk electronic band structure and electronic density of states features. Both electronic band structure and optical constants show clear indications of a direct band gap of 0.61 eV for Bi2Te2Se. Bi2Te2Se possesses high refractive index at low photon energies in the infrared and visible region. It has low reflectivity in the ultraviolet region. Bi2Te2Se absorbs photons strongly in the ultraviolet energies. All these characteristics make Bi2Te2Se suitable for diverse class of optoelectronic device applications.