Valley switch in a graphene superlattice due to pseudo-Andreev reflection
Beenakker, C. W. J. and Gnezdilov, N. V. and Dresselhaus, E. and Ostroukh, V. P. and Herasymenko, Y. and Adagideli, İnanç and Tworzydło, J. (2018) Valley switch in a graphene superlattice due to pseudo-Andreev reflection. Physical Review B: Condensed Matter and Materials Physics, 97 (24). ISSN 1098-0121 (Print) 1550-235X (Online)
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Official URL: http://dx.doi.org/10.1103/PhysRevB.97.241403
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.
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