Landau polaritons in highly non-parabolic 2D gases in the ultra-strong coupling regime

TL;DR

This study explores ultra-strong light-matter coupling in highly non-parabolic 2D electron and hole gases, revealing a novel lower polaritonic gap that deviates from traditional models.

Contribution

It demonstrates the first observation of a lower polaritonic gap in highly non-parabolic 2D gases under ultra-strong coupling conditions.

Findings

Observation of a lower polaritonic gap in non-parabolic systems

Comparison between non-parabolic and parabolic quantum wells

Tuning coupling strength via lithography and optical pumping

Abstract

We probe ultra-strong light matter coupling between metallic terahertz metasurfaces and Landau-level transitions in high mobility 2D electron and hole gases. We utilize heavy-hole cyclotron resonances in strained Ge and electron cyclotron resonances in InSb quantum wells, both within highly non-parabolic bands, and compare our results to well known parabolic AlGaAs/GaAs quantum well (QW) systems. Tuning the coupling strength of the system by two methods, lithographically and by optical pumping, we observe a novel behavior clearly deviating from the standard Hopfield model previously verified in cavity quantum electrodynamics: an opening of a lower polaritonic gap.