Anisotropic Supercurrent in Strained Graphene Josephson Junction

Abstract

The Weyl-Dirac fermions in graphene-based SG/I/SG (SG denoting superconducting graphene; I, an insulator) junctions subjected to strains become highly asymmetric. The effect of the strain-induced symmetry change of the fermions on the supercurrent is studied. The highly anisotropic velocity near the critical deformation causes the critical current parallel to the direction of strain to oscillate as a function of gate voltage at a very high frequency. The same anisotropic velocity destroys the oscillation of the gate-dependent critical current when the current is perpendicular to the direction of strain. The directiondependent supercurrent is due to the strain turning the twodimensional massless relativistic electrons into nearly onedimensional massless relativistic fermions near the critical deformation. This work reveals that a new effect can be induced by applying strain on a graphene-based Josephson junction.

Generalized Hamiltonian for a graphene subjected to arbitrary in-plane strains

“…150 There are two ways to realize the strain-modulated graphene Josephson junction. One is the uniform strain for the whole graphene superconductor junction including the left and right graphene superconducting regions, [151][152][153] and the other is the non-uniform strain only applied inside some local regions. 154 For the uniform strain, the whole sheet of graphene has the same deformation and thus there is no mismatch of the wave vectors of the wave functions between the superconducting region and the normal region.…”