Strain induced topological phase transition at zigzag edges of monolayer transition-metal dichalcogenides

TL;DR

This paper investigates how strain influences topological phases and Majorana zero modes in zigzag edges of monolayer transition-metal dichalcogenides with induced superconductivity, revealing strain as a tunable parameter for topological control.

Contribution

It demonstrates that strain can induce a topological phase transition, either destroying or tuning Majorana modes, and connects these effects to the multi-band Berry phase as a topological invariant.

Findings

Strain shifts edge state energies, causing topological phase transitions.

Small built-in strain can destroy Majorana modes.

Strain can be used to manipulate Majorana zero modes via Zeeman field.

Abstract

The effect of strain in zigzag ribbons of monolayer transition-metal dichalcogenides with induced superconductivity is studied using a minimal 3-band tight-binding model. The unstrained system shows a topological phase with Majorana zero modes localized at the boundaries of the one-dimensional (1D) zigzag edges. By direct inspection of the spectrum and wave functions we examine the evolution of the topological phase as an in-plane, uniaxial deformation is imposed. It is found that strain shifts the energy of 1D edge states, thus causing a topological phase transition which eliminates the Majorana modes. For realistic parameter values, we show that the effect of strain can be changed from completely destructive -- in which case a small built in strain is enough to destroy the topological phase -- to a situation where strain becomes an effective tuning parameter which can be used to manipulate Majorana zero modes. These two regimes are accessible by increasing the value of the applied Zeeman field within realistic values. We also study how strain effects are affected by the chemical potential, showing in particular how unwanted effects can be minimized. Finally, as a cross-check of the obtained results, we reveal the connection between 1D Majorana zero modes in the zigzag edge and the multi-band Berry phase, which serves as a topological invariant of this system.