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Achieving a population imbalance between the two inequivalent valleys is acritical first step for any valleytronic device. A valley-polarization can beinduced in biased bilayer graphene using circularly polarized light. In thispaper, we present a detailed theoretical study of valley-polarization in biasedbilayer graphene. We show that a nearly perfect valley-polarization can beachieved with the proper choices of external bias and pulse frequency. We findthat the optimal pulse frequency $\omega$ is given by $\hbar\omega=2a,$ where$2a$ is the potential energy difference between the graphene layers. We alsofind that the valley-polarization originates not from the Dirac pointsthemselves, but rather from a ring of states surrounding each. Intervalleyscattering is found to greatly reduce the valley-polarization for highfrequency pulses. Thermal populations are found to significantly reduce thevalley-polarization for small biases. This work provides insight into theorigin of valley-polarization in bilayer graphene and will aid experimentalistsseeking to study valley-polarization in the lab.

Valley-polarization in biased bilayer graphene using circularly polarized light