Valley-controlled nonlocal transistor based on irradiated and biased bilayer graphene

Abstract

We theoretically study the nonlocal Andreev transport through a normal/superconducting/normal junction formed on bilayer graphene, in which an off-resonant circularly polarized light and interlayer biases are applied to the two normal regions. The effects of the light field, bias voltage, and superconductor length on the crossed Andreev reflection are calculated and analyzed. We show that the pure crossed Andreev reflection can be obtained by modulating the completely opposite valley polarizations in the two terminals under the optical and electrical coaction, and a valley-switch effect can be realized between the pure crossed Andreev reflection and the pure valley polarized elastic cotunneling by reversing the interlayer bias of one terminal. In addition, a very small subthreshold swing can be acquired when the pure nonlocal conductance changes with variation of the Fermi energy. This observation suggests that our device can be operated as a fast nonlocal switching transistor.