Valley-polarization in biased bilayer graphene using circularly polarized light

Abstract

Achieving a population imbalance between the two inequivalent valleys is a critical first step for any valleytronic device. A valley-polarization can be induced in biased bilayer graphene using circularly polarized light. In this paper, we present a detailed theoretical study of valley-polarization in biased bilayer graphene. We show that a nearly perfect valley-polarization can be achieved with the proper choices of external bias and pulse frequency. We find that the optimal pulse frequency $\omega$ is given by $\hslash \omega =2a,$ where $2a$ is the potential energy difference between the graphene layers. We also find that the valley-polarization originates not from the Dirac points themselves, but rather from a ring of states surrounding each. Intervalley scattering is found to greatly reduce the valley-polarization for high frequency pulses. Thermal populations are found to significantly reduce the valley-polarization for small biases. This work provides insight into the origin of valley-polarization in bilayer graphene and will aid experimentalists seeking to study valley-polarization in the lab.

18 pages, 9 figures, v2: elaboration and readability improvements

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Cited by in corpus (13)

• Controlling Valley-Polarisation in Graphene via Tailored Light Pulses
• Valley Degree of Freedom in Two-Dimensional van der Waals Materials
• Intense-pulse dynamics of massless Dirac electrons
• Ultrafast valley polarization in bilayer graphene
• Valley polarization, magnetization, and superconductivity in bilayer graphene near the van Hove singularity
• Effectuating tunable valley selection via multi-terminal monolayer graphene devices
• Topological frequency conversion in rhombohedral multilayer graphene
• Energy symmetry and interlayer wave function ratio of tunneling electrons in partially overlapped graphene
• Energy magnetization and transport in systems with a non-zero Berry curvature in a magnetic field
• All-electrical scheme for valley polarization in graphene
• Evanescent-mode-assisted Klein tunneling in dual-gated bilayer graphene
• Ultrafast Saddletronics
• The impact of nitrogen doping on the linear and nonlinear terahertz response of graphene