New supercurrent pattern in quantum point contact with strained graphene nanoribbon

TL;DR

This paper theoretically investigates the Josephson effect in strained zigzag graphene nanoribbons, revealing unique supercurrent quantization, step-wise width dependence, and potential for strain-controlled supercurrent switching.

Contribution

It introduces a novel understanding of supercurrent behavior in strained graphene nanoribbons, highlighting strain-induced quantization and the possibility of supercurrent control via strain.

Findings

Step-wise variation of critical supercurrent with nanoribbon width.

Quantization of supercurrent influenced by strain and pseudospin coupling.

Potential for strain-controlled supercurrent switching.

Abstract

We theoretically reveal the unusual features of the Josephson effect in a strained zigzag graphene nanoribbon with a small length relative to the superconducting coherence length and an arbitrary width. We find a step-wise variation of the critical supercurrent with the width of the nanoribbon, showing additional small width plateaus placed between the broad steps of a unstrained structure. We further demonstrate the peculiar quantization of the critical supercurrent in terms of the strain, resulted from the coupling of the pseudospin of Dirac fermions with the strain-induced gauge potential, where the height of the steps decreases with growing the strength of the fictitious gauge potential. Moreover, our results determine the potential of the proposed superconducting quantum point contact for the realization of the supercurrent switch under an applied strain. Besides, we find the local density of states of the strained zigzag nanoribbon displays a crossover between the decaying and oscillating behavior with the distance from the edges, by tuning the width and Fermi wavelength of the nanoribbon.