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

• Published in: Physical review. B 2016-11, Vol.94 (19), Article 195419
• Main Authors: Li, Linhu, Castro, Eduardo V., Sacramento, Pedro D.
• Format: Article
• Language: English
• Subjects: Chalcogenides; Chemical potential; Deformation mechanisms; Inspection; Monolayers; Organic chemistry; Parameters; Phase transitions; Ribbons; Superconductivity; Tapes (metallic); Transition metal compounds; Wave functions
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.94.195419

The effect of strain in zigzag ribbons of monolayer transition-metal dichalcogenides with induced superconductivity is studied using a minimal three-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 multiband Berry phase, which serves as a topological invariant of this system.