The superradiant phase is a finite size effect in two-photon processes

TL;DR

This paper demonstrates that the superradiant phase observed in two-photon systems is a finite-size effect and does not persist in the thermodynamic limit, clarifying its true nature.

Contribution

The study provides analytical and numerical evidence that the superradiant phase in the two-photon Dicke model is a finite-size phenomenon, not a genuine thermodynamic phase.

Findings

Superradiant phase shrinks with increasing system size

Superradiant phase disappears in the thermodynamic limit

Spectral collapse remains in the thermodynamic limit

Abstract

Two-photon light-matter interactions exhibit distinctive features such as spectral collapse. The two-photon Dicke model has been reported to exhibit a superradiant phase which could be useful in quantum applications. Here we show that this superradiant phase is not a genuine thermodynamic phase but a finite-size effect. Combining analytical and numerical analyses, we demonstrate that the superradiant region shrinks with increasing system size and disappears in the thermodynamic limit, while spectral collapse remains. Our results clarify the nature of superradiant conditions in two-photon systems and constrain its realization in quantum platforms.