Dirac fermion optics and directed emission from single- and bilayer graphene cavities

TL;DR

This paper explores Dirac fermion optics in graphene cavities, demonstrating tunable emission and confinement effects influenced by cavity shape, layer number, and source position, with potential applications in electron optics.

Contribution

It introduces a detailed analysis of Dirac fermion resonant states in graphene micro-cavities, highlighting the effects of Klein tunneling and cavity design on emission properties.

Findings

Distinct emission profiles for single- and bilayer graphene due to Klein tunneling.

Strong charge carrier confinement and lensing effects observed in simulations.

Emission characteristics depend on source position in single-layer graphene, less so in bilayer.

Abstract

High-mobility graphene hosting massless charge carriers with linear dispersion provides a promising platform for electron optics phenomena. Inspired by the physics of dielectric optical micro-cavities where the photon emission characteristics can be efficiently tuned via the cavity shape, we study corresponding mechanisms for trapped Dirac fermionic resonant states in deformed micro-disk graphene billiards and directed emission from those. In such graphene devices a back-gate voltage provides an additional tunable parameter to mimic different effective refractive indices and thereby the corresponding Fresnel laws at the boundaries. Moreover, cavities based on single-layer and double-layer graphene exhibit Klein- and anti-Klein tunneling, respectively, leading to distinct differences with respect to dwell times and resulting emission profiles of the cavity states. Moreover, we find a variety of different emission characteristics depending on the position of the source where charge carriers are fed into the cavites. Combining quantum mechanical simulations with optical ray tracing and a corresponding phase-space analysis, we demonstrate strong confinement of the emitted charge carriers in the mid field of single-layer graphene systems and can relate this to a lensing effect. For bilayer graphene, trapping of the resonant states is more efficient and the emission characteristics do less depend on the source position.