Discrete Symmetry Breaking Transitions Between Paired Superfluids

TL;DR

This paper investigates phase transitions between paired superfluids in one-dimensional bosonic systems with Feshbach interactions, identifying an Ising quantum phase transition through numerical and theoretical analysis.

Contribution

It provides the first detailed characterization of the Ising transition in 1D bosonic superfluids with pairing interactions using DMRG and field theory methods.

Findings

Identification of an Ising quantum phase transition

Correlation functions reveal critical properties

Absence of a purely atomic superfluid phase

Abstract

We explore the zero-temperature phase diagram of bosons interacting via Feshbach resonant pairing interactions in one dimension. Using DMRG (Density Matrix Renormalization Group) and field theory techniques we characterize the phases and quantum phase transitions in this low-dimensional setting. We provide a broad range of evidence in support of an Ising quantum phase transition separating distinct paired superfluids, including results for the energy gaps, correlation functions and entanglement entropy. In particular, we show that the Ising correlation length, order parameter and critical properties are directly accessible from a ratio of the atomic and molecular two-point functions. We further demonstrate that both the zero-momentum occupation numbers and the visibility are in accordance with the absence of a purely atomic superfluid phase. We comment on the connection to recent studies of boson pairing in a generalized classical XY model.