Strain induced band-gap tailoring in SeO and TeO topological insulators

Abstract

In this work we present first principles study of structural, electronic, and optical properties of oxygen functionalized selenene and tellurene using density functional theory (DFT). SeO and TeO monolayers show direct band gap opening at K- point under spin orbit coupling (SOC), in which, we have achieved further expansion by applying moderate compressive/tensile strain to improve suitability for optoelectronics application. During this process Dirac cone like structure remains protected in both monolayers validating topological insulator phase transition with broken spatial inversion symmetry. The band gap values of these monolayers imply that they might be beneficial in infrared (IR) detection and are excellent candidates for THz-IR photo detector applications. In addition to this we explore optical properties such as dielectric functions, absorption coefficients, refractive index, extinction coefficient and reflectivity within generalized gradient approximation (GGA) between energy-range of 0 eV–20 eV of both monolayers. High value of real part of dielectric function, refractive index and absorption coefficient in IR spectral region, suggest usefulness of both materials as topological insulators for dielectric nanophotonics.