Electronic band tuning under pressure in MoTe₂ topological semimetal

Topological superconductors (TSC) can host exotic quasiparticles such as Majorana fermions, poised as the fundamental qubits for quantum computers. TSC’s are predicted to form a superconducting gap in the bulk, and gapless surface/edges states which can lead to the emergence of Majorana zero energy modes. A candidate TSC is the layered dichalcogenide MoTe₂, a type-II Weyl (semi)metal in the non-centrosymmetric orthorhombic (T_d) phase. It becomes superconducting upon cooling below 0.25 K, while under pressure, superconductivity extends well beyond the structural boundary between the orthorhombic and monoclinic (1T′) phases. Here, we show that under pressure, coupled with the electronic band transition across the T_d to 1T′ phase boundary, evidence for a new phase, we call T_d* is observed and appears as the volume fraction of the T_d phase decreases in the coexistence region. T_d* is most likely centrosymmetric. In the region of space where T_d* appears, Weyl nodes are destroyed. T_d* disappears upon entering the monoclinic phase as a function of temperature or on approaching the suppression of the orthorhombic phase under pressure above 1 GPa. Our calculations in the orthorhombic phase under pressure show significant band tilting around the Weyl nodes that most likely changes the spin-orbital texture of the electron and hole pockets near the Fermi surface under pressure that may be linked to the observed suppression of magnetoresistance with pressure.