Strain-gradient induced topological transition in bent nanoribbons of the Dirac semimetal Cd3As2

TL;DR

This paper demonstrates how applying a strain gradient to bent Cd3As2 nanoribbons induces a topological phase transition by breaking symmetry and opening an energy gap at Dirac points, enabling control over topological states.

Contribution

It provides an experimental method to induce and study topological phase transitions in Dirac semimetal nanoribbons through strain engineering.

Findings

Strain gradient causes lattice deformation and breaks C4 symmetry.

Energy gap opens at Dirac points due to strain-induced symmetry breaking.

Strain gradient influences the evolution of energy band structures.

Abstract

Dirac semimetal is an ideal parent state to realize various exotic states of matters, such as quantum spin Hall state, Weyl semimetal phase and Majorana zero modes. Topological phase transition allows for the switching between these different topological states. Here, in this paper, we exhibit experimentally an effective approach of inducing topological phase transition in Cd3As2 nanoribbons, by applying a bending strain profile onto the sample. The local strain varies linearly from compression to tension through the cross-section of a bent nanoribbon. The strain gradient causes obvious lattice deformation and breaks the C4 rotational symmetry, thus opening an energy gap at the Dirac points and making the bulk gapful. When further increasing the strain strength, the local strain effect dominates over the symmetry-breaking effect, where spatially-varying band shift becomes prominent across the nanoribbon. Our results demonstrate the effect of strain gradient on the evolution of energy band structures, which should be valuable for further study of strain-mediated topological phase transition.