Valley switch in a graphene superlattice due to pseudo-Andreev reflection

Abstract

In valleytronics, one seeks to employ the valley index of Dirac electrons in graphene as a carrier of information. This work shows that reflection from a superlattice potential can provide a valley switch: electrons in valley $K$ approaching the superlattice near normal incidence are reflected into valley ${K}^{\ensuremath{'}}$. The authors identify the topological origin of this effect, by mapping onto Andreev reflection from a topological superconductor. The valley switch is ideal at a symmetry point of the superlattice potential, yet remains close to 100% over a broad parameter range.