Optical dressing of the electronic response of two-dimensional semiconductors in quantum and classical descriptions of cavity electrodynamics

TL;DR

This paper investigates how light-matter interactions in two-dimensional semiconductors within optical cavities can be described by classical and quantum models, revealing that classical descriptions suffice even in strong coupling regimes for certain electronic properties.

Contribution

It demonstrates that classical light descriptions can accurately capture the electronic response modifications in 2D semiconductors inside cavities, even under strong coupling conditions.

Findings

Spectral weight shifts at resonant frequencies indicate light-matter hybridization.

Classical models explain photon dressing effects up to strong coupling regimes.

Quantum corrections are negligible and mainly due to off-resonant high-energy photon modes.

Abstract

We study quantum effects of the vacuum light-matter interaction in materials embedded in optical cavities. We focus on the electronic response of a two-dimensional semiconductor placed inside a planar cavity. By using a diagrammatic expansion of the electron-photon interaction, we describe signatures of light-matter hybridization characterized by large asymmetric shifts of the spectral weight at resonant frequencies. We follow the evolution of the light-dressing from the cavity to the free-space limit. In the cavity limit, light-matter hybridization results in a modification of the optical gap with sizeable spectral weight appearing below the bare gap edge. In the limit of large cavities, we find a residual redistribution of spectral weight which becomes independent of the distance between the two mirrors. We show that the photon dressing of the electronic response can be fully explained by using a classical description of light. The classical description is found to hold up to a strong coupling regime of the light-matter interaction highlighted by the large modification of the photon spectra with respect to the empty cavity. We show that, despite the strong coupling, quantum corrections are negligibly small and weakly dependent on the cavity confinement. As a consequence, in contrast to the optical gap, the single particle electronic band gap is not sensibly modified by the strong-coupling. Our results show that quantum corrections are dominated by off-resonant photon modes at high energy. As such, cavity confinement can hardly be seen as a knob to control the quantum effects of the light-matter interaction in vacuum.