Light-matter decoupling in the deep strong coupling regime: The breakdown of the Purcell effect

TL;DR

This paper demonstrates that in the deep strong coupling regime of cavity QED, light and matter can decouple, reversing the Purcell effect and reducing spontaneous emission rates despite increased coupling strength.

Contribution

It reveals the breakdown of the light-matter coupling paradigm at very high coupling strengths, showing a decoupling phenomenon and its impact on emission rates.

Findings

Light and matter decouple in the deep strong coupling regime.

The Purcell effect is reversed at high coupling strengths.

Spontaneous emission rate decreases despite stronger coupling.

Abstract

Improvements both in the photonic confinement and in the emitter design have led to a steady increase in the strength of the light-matter coupling in cavity quantum electrodynamics experiments. This has allowed to access interaction-dominated regimes in which the state of the system can only be described in terms of mixed light-matter excitations. Here we show that, when the coupling between light and matter becomes strong enough, this picture breaks down, and light and matter degrees of freedom totally decouple. A striking consequence of such a counter-intuitive phenomenon is that the Purcell effect is reversed and the spontaneous emission rate, usually thought to increase with the light-matter coupling strength, plummets instead for large enough couplings.