title: van der Waals Stacking-Induced Topological Phase Transition in Layered Ternary Transition Metal Chalcogenides.
abstract: Novel materials with nontrivial electronic and photonic band topology are crucial for realizing novel devices with low power consumption and heat dissipation and quantum computing free of decoherence. Here, we theoretically predict a novel class of ternary transition metal chalcogenides that exhibit dual topological characteristics, quantum spin Hall insulators (QSHIs) in their two-dimensional (2D) monolayers and topological Weyl semimetals in their 3D noncentrosymmetric crystals upon van der Waals (vdW) stacking. Remarkably, we find that one can create and annihilate Weyl fermions and realize the transition between Type-I and Type-II Weyl fermions by tuning vdW interlayer spacing, providing the missing physical picture of the evolution from 2D QSHIs to 3D Weyl semimetals. Our results also show that these materials possess excellent thermodynamic stability and weak interlayer binding; some of them were synthesized two decades ago, implying their great potentials for experimental synthesis, characterization, and vdW heterostacking. Moreover, their ternary nature will offer more tunability for electronic structure by controlling different stoichiometry and valence charges. Our findings provide an ideal materials platform for realizing QSH effect and exploring fundamental topological phase transition and will open up a variety of new opportunities for two-dimensional materials and topological materials research.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Junwei
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, College of Engineering and College of Science, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Fang
authors.affiliation: Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Liang
authors.initials: L
authors.lastname: Fu
authors.affiliation: Department of Materials Science and Engineering, College of Engineering and College of Science, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Xiaofeng
authors.identifier: 0000-0003-1627-288X
authors.initials: X
authors.lastname: Qian
keywords: 2D materials; Quantum spin Hall insulators; Weyl semimetals; ternary transition metal chalcogenides; topological phase transition