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

C. W. J. Beenakker; N. V. Gnezdilov; E. Dresselhaus; V. P. Ostroukh; Y. Herasymenko; İ. Adagideli; J. Tworzydło

doi:10.1103/PhysRevB.97.241403

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

C. W. J. Beenakker, N. V. Gnezdilov, E. Dresselhaus, V. P. Ostroukh, Y. Herasymenko, İ. Adagideli, J. Tworzydło

DOI 10.1103/PhysRevB.97.241403 · Physical Review B

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Abstract

Dirac electrons in graphene have a valley degree of freedom that is being explored as a carrier of information. In that context of “valleytronics” one seeks to coherently manipulate the valley index. Here, we show that reflection from a superlattice potential can provide a valley switch: Electrons approaching a pristine-graphene–superlattice-graphene interface near normal incidence are reflected in the opposite valley. We identify the topological origin of this valley switch, by mapping the problem onto that of Andreev reflection from a topological superconductor, with the electron-hole degree of freedom playing the role of the valley index. The valley switch is ideal at a symmetry point of the superlattice potential, but remains close to 100% in a broad parameter range.