Ab initio approach to the elastic, electronic, and optical properties of MoTe2: A topological Weyl semimetal

Abstract

The topological Weyl semimetal MoTe2, in the orthorhombic phase, is an important system both from the point of view of fundamental physics and potential applications. In this study we have investigated the elastic, electronic, bonding and optical properties of MoTe2 using density functional theory. Study of the elastic constants and moduli indicates that MoTe2 is a relatively soft material with high level of machinability. Mechanical stability conditions are fulfilled. The compound possesses elastic and mechanical anisotropy and is prone to brittle fracture. Elastic parameters indicate that both covalent and metallic bondings are present in MoTe2. This is supported by the charge density distribution mapping and Mulliken and Hirshfeld bond population analyses. Debye temperature has been calculated. A relatively low value of Debye temperature also supports the scenario where bonding strengths are weak. The bulk electronic band structure calculations reveal clear indications of semi-metallic character. A pseudogap in the electronic energy density of states at the Fermi level indicates high level of electronic stability. Features reminiscent of the Dirac cone is observed close to the Fermi level. There is significant electronic anisotropy. Bands running in the crystallographic c-direction are non-dispersive with high carrier effective mass. Investigation of optical constants demonstrate that MoTe2 possess excellent reflecting characteristics over a wide spectral range encompassing the infrared to ultraviolet regions. The compound also has high refractive index in the visible range. MoTe2 is optically anisotropic, reflecting the anisotropic nature of the electronic band structure. The energy dependent optical parameters show metallic features and are in complete accord with the electronic density of states calculations.