Quantum decoupling transition in a one-dimensional Feshbach-resonant superfluid

TL;DR

This paper investigates a one-dimensional fermionic gas with Feshbach resonance, revealing a quantum phase transition where atomic and molecular superfluids decouple due to quantum fluctuations, with distinct experimental signatures.

Contribution

It demonstrates a unique quantum decoupling transition in 1D superfluids, contrasting higher-dimensional behavior, and predicts observable experimental effects.

Findings

Identification of a quantum phase transition leading to decoupling of superfluids.

Emergence of an out-of-phase gapless mode in the decoupled phase.

Discontinuous change in molecular momentum distribution function.

Abstract

We study a one-dimensional gas of fermionic atoms interacting via an s-wave molecular Feshbach resonance. At low energies the system is characterized by two Josephson-coupled Luttinger liquids, corresponding to paired atomic and molecular superfluids. We show that, in contrast to higher dimensions, the system exhibits a quantum phase transition from a phase in which the two superfluids are locked together to one in which, at low energies, quantum fluctuations suppress the Feshbach resonance (Josephson) coupling, effectively decoupling the molecular and atomic superfluids. Experimental signatures of this quantum transition include the appearance of an out-of-phase gapless mode (in addition to the standard gapless in-phase mode) in the spectrum of the decoupled superfluid phase and a discontinuous change in the molecular momentum distribution function.