Turning the BEC-BCS crossover into a transition by radiation

TL;DR

This paper demonstrates that radio frequency radiation can induce a non-equilibrium phase transition in the BCS-BEC crossover, transforming the BCS phase into a supersolid while leaving the BEC phase unchanged, with implications for quantum phase control.

Contribution

It establishes a formal distinction between BCS and BEC phases via fermionic excitation spectra and shows radiation-induced phase transition from BCS to supersolid in 2D systems.

Findings

Radio frequency radiation induces a phase transition in the BCS-BEC crossover.

The BEC phase remains translationally invariant under radiation.

The BCS phase transforms into a supersolid phase under radiation.

Abstract

We show that the Bardeen-Cooper-Schrieffer state (BCS) and the Bose-Einstein condensation (BEC) sides of the BCS-BEC crossover can be rigorously distinguished from each other by the extrema of the spectrum of the fermionic excitations. Moreover, we demonstrate that this formal distinction is realized as a non-equilibrium phase transition under radio frequency radiation. The BEC phase remains translationally invariant, whereas the BCS phase transforms into the supersolid phase. For a two-dimensional system this effect occurs at arbitrary small amplitude of the radiation field.