Valley engineering by strain in Kekul\'e-distorted graphene

TL;DR

This paper investigates how uniaxial strain affects the electronic band structure of Kekule9-distorted graphene, revealing strain-induced valley separation and potential control of intervalley scattering, with implications for valleytronics.

Contribution

It provides a detailed analysis of strain effects on Kekule9-distorted graphene, introducing a tight-binding model and analytical expressions that describe valley separation and gap modulation.

Findings

Strain induces a Zeeman-like pseudospin coupling separating valleys.

In Kek-O phase, strain can close the strain-induced gap.

In Kek-Y phase, strain shifts Dirac cones, enabling valley control.

Abstract

A Kekul\'e bond texture in graphene modifies the electronic band structure by folding the Brillouin zone and bringing the two inequivalent Dirac points to the center. This can result, in the opening of a gap (Kek-O) or the locking of the valley degree of freedom with the direction of motion (Kek-Y). We analyze the effects of uniaxial strain on the band structure of Kekul\'e-distorted graphene for both textures. Using a tight-binding approach, we introduce strain by considering the hopping renormalization and corresponding geometrical modifications of the Brillouin zone. We numerically evaluate the dispersion relation and present analytical expressions for the low-energy limit. Our results indicate the emergence of a Zeeman-like term due to the coupling of the pseudospin with the pseudomagnetic strain potential which separates the valleys by moving them in opposite directions away from the center of the Brillouin zone. For the Kek-O phase, this results in a competition between the Kekul\'e parameter that opens a gap and the magnitude of strain which closes it. While for the Kek-Y phase, in a superposition of two shifted Dirac cones. As the Dirac cones are much closer in the supperlattice reciprocal space that in pristine graphene, we propose strain as a control parameter for intervalley scattering.