Prediction of topological nontrivial semimetals and pressure-induced Lifshitz transition in 1T′-MoS2 layered bulk polytypes

Abstract

Recently, bulk MoS₂ crystals stacked by 1T′-MoS₂ monolayers have been synthesized successfully, but little is known about their stacking sequences and topological properties. Based on first-principles calculations and symmetry-based indicator theory, we discovered that three predicted bulk structures of MoS₂ (named 2M-, 1T′- and β-MoS₂) stacked by 1T′ monolayers are topological insulators and nodal line semimetals with and without spin–orbit coupling. Their stacking stability, electronic structure and the topology origin were systematically investigated. Further research proves that in the absence of SOC the open- and closed-type nodal lines can coexist in the momentum space of 2M-MoS₂, which also possesses drumhead-like surface state. Moreover, we predicted a pressure-induced Lifshitz transition at about 1.3 GPa in 2M-MoS₂. Our findings greatly enrich the topological phases of MoS₂ and probably bring MoS₂ to the rapidly growing family of layered topological semimetals.