Evolution of Weyl fermions along the polarity reversal paths in MoTe₂

MoTe₂ is a layered material with rich physics arising from structural and electronic phase competition. The three observed crystal phases - 2H, 1T′, and T_d - have distinct electronic properties. The non-centrosymmetric T_d -MoTe₂ is particularly fascinating due to the presence of type-I and type-II Weyl nodes in this system. In this study, we investigate the energetics of the possible structural phase transitions in MoTe₂, and explore the possibility of controlling the dynamics of Weyl fermions in MoTe₂. Our first-principles calculations reveal that one can systematically tune the location and chirality of Weyl nodes by exploiting the connection between polar distortions and spin-orbit coupling effects in T_d - MoTe₂. By restoring the broken inversion symmetry, we locate a highly symmetric saddle point structure (T_d⁰) on the energy landscape of MoTe₂, establishing a polarity reversal path connecting up and down variants of T_d. The T_d⁰ phase resembles a paraelectric phase of a ferroelectric compound, and it is dynamically and elastically unstable leading to structural phase transitions into the T_d and 1T′ phases. We study the evolution of Weyl nodes as a function of structural distortions in the vicinity of T_d⁰.