Cone-dependent retro- and specular Andreev reflections in AA-stacked bilayer graphene

Abstract

We theoretically study the Andreev reflection (AR) in AA-stacked bilayer graphene-superconductor junction. AABG has a linear gapless energy band with two shifted Dirac cones and the electronic states are described by the cone indices. The results indicate that the property of AR strongly depends on the cone degree of freedom. In the absence of the interlayer potential difference, only intracone AR and normal reflection (NR) could occur, and the intercone process is forbidden. By adjusting the potential, the intracone AR can be specular AR (SAR) in one cone and it is retro-AR (RAR) in the other cone. The existence of the interlayer potential difference would lead to the intercone scattering. As a result, double ARs and double NRs can take place between the two cones. The intercone SAR could happen in a broad potential region. Furthermore, the intercone retro-NR (RNR) could happen as well. The switch between SAR and RAR, and the switch between specular NR (SNR) and RNR can be achieved by regulating the potential. Therefore, different cone carriers can be separated spatially based on the RAR and SAR. The cone-dependent Andreev conductance may be separately measured near the critical values where RAR crosses over to SAR.

Similar papers