Nonlocal effects and enhanced nonreciprocity in current-driven graphene systems

TL;DR

This paper explores how the intrinsic nonlocal response of graphene affects current-driven plasmons, demonstrating that unidirectional, backscattering-immune modes can still be supported and enhanced through pairing graphene sheets.

Contribution

It provides a detailed theoretical analysis of nonlocal effects on graphene plasmons under current bias, revealing mechanisms to boost nonreciprocity and optical isolation.

Findings

Nonlocal effects weaken spectral asymmetry but still support unidirectional modes.

Drift current can pump plasmons and extend their propagation distance.

Pairing graphene sheets enhances nonreciprocity and optical isolation.

Abstract

A graphene sheet biased with a drift electric current offers a tantalizing opportunity to attain unidirectional, backscattering-immune, and subwavelength light propagation, as proposed in [T. A. Morgado, M. G. Silveirinha, ACS Photonics 5(11), 4253 (2018)]. Here, we investigate in detail the impact of the intrinsic nonlocal response of graphene in the dispersion characteristics of the current-driven plasmons supported by single-layer and double-layer graphene systems. It is theoretically shown that even though the nonlocal effects weaken the spectral asymmetry of the plasmons dispersion, the studied platforms can support unidirectional backscattering-immune guided modes. Our analysis also confirms that the drift-current bias can effectively pump the graphene plasmons and enhance the propagation distance. Moreover, it is shown that the nonreciprocity and optical isolation can be boosted by pairing two drift-current biased graphene sheets due to the enhanced radiation drag by the drifting electrons.