Van der Waals Stacking Induced Topological Phase Transition in Layered Ternary Transition Metal Chalcogenides

TL;DR

This paper predicts a new class of layered ternary transition metal chalcogenides that exhibit dual topological phases, including quantum spin Hall insulators and Weyl semimetals, with tunable topological transitions via van der Waals stacking.

Contribution

It introduces a novel class of ternary transition metal chalcogenides with dual topological phases and demonstrates tunable topological phase transitions through vdW stacking.

Findings

MM'Te4 exhibits quantum spin Hall and Weyl semimetal phases.

Weyl fermions can be created, annihilated, and tuned between Type-I and Type-II.

Materials are thermodynamically stable with weak interlayer binding.

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 using first-principles approach, we predict a class of ternary transition metal chalcogenides (TTMC) MM'Te$_4$ exhibits dual topological characteristics: quantum spin Hall (QSH) insulators in their 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. Our calculations show that they possess excellent thermodynamic stability and weak interlayer binding, implying their great potentials for experimental synthesis, direct exfoliation 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 topological phase transition, and will open up a variety of new opportunities for two-dimensional materials and topological materials research.