Evidence for Topological States and a Lifshitz Transition in Metastable 2<i>M</i>‐WSe₂

Abstract In recent years, T d transition metal dichalcogenides have been heavily explored for their type‐II Weyl topology, gate‐tunable superconductivity, and nontrivial edge states in the monolayer limit. Here, the Fermi surface characteristics and fundamental transport properties of similarly structured 2 M ‐WSe 2 bulk single crystals are investigated. The measurements of the angular dependent Shubnikov–de Haas oscillations, with support from first‐principles calculations, reveal multiple three‐ and two‐dimensional Fermi pockets, one of which exhibits a nontrivial Berry's phase. In addition, it is shown that the electronic properties of 2 M ‐WSe 2 are similar to those of orthorhombic MoTe 2 and WTe 2 , having a single dominant carrier type at high temperatures that evolves into coexisting electron and hole pockets with near compensation at temperatures below 100 K, suggesting the existence of a Lifshitz transition. Altogether, the observations provide evidence towards the topologically nontrivial electronic properties of 2 M ‐WSe 2 and motivate further investigation on the topological properties of 2 M transition metal dichalcogenides in the atomically thin limit.