Fast electrically switchable large gap quantum spin Hall states in MGe$_2$Z$_4$

TL;DR

This paper predicts a new 2D material family with large, tunable quantum spin Hall gaps that can be rapidly switched using electric fields, promising for low-power quantum devices.

Contribution

It introduces a new 2D material family with large, switchable QSH states and demonstrates their electric field tunability via first-principles calculations.

Findings

Large band gap (~237 meV) in 1T'-MoGe2Z4 monolayers.

Electric field induces a phase transition from QSH to trivial insulator.

Rapid topological switching potential for quantum device applications.

Abstract

Spin-polarized conducting edge currents counterpropagate in quantum spin Hall (QSH) insulators and are protected against disorder-driven localizations by the time-reversal symmetry. Using these spin-currents for device applications require materials having large band gap and fast switchable QSH states. By means of in-depth first-principles calculations, we demonstrate the large band gap and fast switchable QSH state in a newly introduced two-dimensional (2D) material family with 1T$^\prime$-MGe$_2$Z$_4$ (M = Mo or W and Z = P or As). The thermodynamically stable 1T$^\prime$-MoGe$_2$Z$_4$ monolayers have a large energy gap around $\sim$237 meV. These materials undergo a phase transition from a QSH insulator to a trivial insulator with a Rashba-like spin splitting under the influence of an out-of-plane electric field, demonstrating the tunability of the band gap and its band topology. Fast topological phase switching in a large gap 1T$^\prime$-MoGe$_2$Z$_4$ QSH insulators has potential applications in low-power devices, quantum computation, and quantum communication.