Cavity modification of magnetoplasmon mode through coupling with intersubband polaritons

TL;DR

This paper explores how coupling a multi-mode cavity to a 2DEG under magnetic field modifies the magnetoplasmon and polaritonic modes, revealing new effects of Coulomb interactions in ultrastrong coupling regimes.

Contribution

It demonstrates cavity-induced modifications of 2DEG responses and introduces a novel method to probe Coulomb interactions through cavity mode reshaping.

Findings

Strong hybridization of TM mode with intersubband transition forming polaritons.

Observation of Coulombic effects linked to inhomogeneous polaritonic modes.

Differential coupling strengths of magnetoplasmon with TE and TM modes.

Abstract

We investigate the coupling of a multi-mode metal-insulator-metal cavity to a two-dimensional electron gas (2DEG) in a quantum well in the presence of a strong magnetic field. The TM cavity mode is strongly hybridized with an intersubband transition of the 2DEG, forming a polaritonic mode in the ultrastrong coupling regime, while the TE mode remains an almost purely cavity mode. The magnetoplasmon excitation emerging from the presence of the magnetic field couples with both TM and TE modes, exhibiting different coupling strengths and levels of spatial field inhomogeneity. While the strong homogeneity of the bare TE mode gives rise to the standard anticrossing of strong coupling, the inhomogeneous polaritonic TM mode is shown to activate an observable Coulombic effect in the spectral response, often referred to as non-locality. This experiment demonstrates a cavity-induced modification of the 2DEG response and offers a new route to probing the effect of Coulomb interactions in ultrastrongly coupled systems via reshaping of their cavity mode profiles.