Pressure Induced Creation and Annihilation of Weyl Points in W_0.5Mo_0.5Te₂

Weyl semimetals (WSM) are an important class of quantum materials in which the low-energy quasi-particle excitations of electrons mimic the features of massless Weyl fermions. Pair creation/annihilation of Weyl fermions has been a subject of much research interest in recent years. In this work, by means of the density-functional theory calculations, we study the role of external pressure and Mo substitution in the widely studied WSM T_d-WTe₂, i.e., W_0.5Mo_0.5Te₂. We find that Weyl nodes slightly shift in the energy space away from the Fermi level as external pressure gradually increases up to 2 GPa. We notice that new pairs of Weyl nodes start appearing through pair-creation mechanism in 2-20 GPa pressure range, yielding as many as 44 Weyl nodes at 20 GPa. Beyond 20 GPa pressure, some pairs of opposite Weyl nodes start annihilating systematically leaving only 16 Weyl points at 35 GPa, which remains invariant until 45 GPa pressure.