Electrically Tunable Interband Collective Excitations in Biased Bilayer and Trilayer Graphene

Abstract

Collective excitations of charged particles under the influence of an electromagnetic field give rise to a rich variety of hybrid light-matter quasiparticles with unique properties. In metals, intraband collective response manifested by negative permittivity leads to plasmon-polaritons with extreme field confinement, wavelength squeezing, and potentially low propagation losses. In contrast, photons in semiconductors commonly couple to interband collective response in the form of exciton polaritons, which give rise to completely different polaritonic properties, described by a superposition of the photon and exciton and an anti-crossing of the eigenstates. In this work, we identify the existence of plasmon-like collective excitations originating from the interband excitonic response of biased bilayer and trilayer graphene, in the form of graphene-exciton-polaritons (GEPs). We find that GEPs possess electrically tunable polaritonic properties and discover that such excitations follow a universal dispersion law for all surface polaritons in 2D excitonic systems. Accounting for nonlocal corrections to the excitonic response, we find that the GEPs exhibit confinement factors that can exceed those of graphene plasmons, and with moderate losses. These predictions of plasmon-like interband collective excitations in biased graphene systems open up new research avenues for tunable polaritonic phenomena based on excitonic systems, and the ability to control and manipulate such phenomena at the atomic scale.

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Cited by in corpus (6)

• The Importance of Pure Dephasing in the Optical Response of Excitons in High-quality van der Waals Heterostructures
• Nanometer-scale Cavities for Mid-infrared Radiation via Image Phonon Polariton Resonators
• Temperature-dependent Optical and Polaritonic Properties of hBN-encapsulated Monolayer TMDs
• The Transmission Line Model for 2D Materials and van der Waals Heterostructures
• Strongly Coupled Exciton--Hyperbolic-phonon-polariton Hybridized States in hBN-encapsulated Biased Bilayer Graphene
• Canalized hyperbolic magnetoexciton polaritons enabled by the Shubnikov-de Haas effect in van der Waals semiconductors