Origin of Structural Phase Transition and Superconductivity in Different Phases of MoTe₂; A First-Principles Study

MoTe₂ has recently attracted much attention due to its rich properties including Weyl Semimetallic (WS) behaviour and superconductivity [1,2]. MoTe₂ exhibits three different phases; 2H, 1T', and T_d. While it is a semiconductor with an indirect band gap of 1.2 eV in the 2H phase, it shows semimetallic and superconducting properties in 1T' and T_d phases. In this talk we discuss the origin of the observed phase transition between monoclinic 1T' phase with inversion symmetry and orthorhombic T_d phase without inversion symmetry (WS candidate) within temperature and pressure (T-P) plane. Our calculations show that these phases are almost degenerate in energy with a very low energy barrier for the transition. The effect of phonon energies and entropy contributions to the phase stability will be presented. We will discuss the electron-phonon coupling and superconductivity in both Weyl-semimetal phase (T_d) and 1T' phases with and without the spin-orbit coupling. A detailed understanding the origin of phase transition between T_d and 1T' phases will allow us to tune the final structure in T-P plane and, in turn, to control the physical properties of these interesting systems.

[1] Y. Qi et al, Nat. Commun. 7, 11038 (2016).
[2] J. Jiang et al., Nat. Commun. 8,13973 (2017).