Abstract
Based on the matrix product states method, we investigate numerically the ground state properties of one-dimensional mixtures of repulsive bosons and spin-imbalanced attractive fermions, the latter being in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where Cooper pairs condense at a finite momentum $k=k_{FFLO}$. We find that the visibility of such a state is dramatically enhanced as the repulsive Bose-Fermi mixture is brought close to the phase-separation point. In particular, large amplitude self-induced oscillations with wave-vector $2k_{FFLO}$ appear in both the fermion total density and the boson density profiles, leaving sharp fingerprints in the corresponding static structure factors. We show that these features remain well visible in cold atoms systems trapped longitudinally by a smooth flat-bottom potential. Hence bosons can be used to directly reveal the modulated Fermi superfluid in experiments.
Highlights
According to the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity, electrons with opposite spin bind into bosonic pairs, which condense in the state of zero centerof-mass momentum, leading to macroscopic phase coherence and vanishing electrical resistance
The 1D FFLO state is signaled by a sharp peak in the pair momentum distribution (PMD) at a finite momentum kFFLO = kF↑ − kF↓, where kF↑ = π N↑/L and kF↓ = π N↓/L are the Fermi momenta of the majority and minority spin components
We have investigated the ground-state properties of a 1D FFLO state coupled to a Bose superfluid through strong repulsive interactions
Summary
According to the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity, electrons with opposite spin bind into bosonic pairs, which condense in the state of zero centerof-mass momentum, leading to macroscopic phase coherence and vanishing electrical resistance. Atomic Bose-Fermi mixtures provide a natural playground for several quantum phenomena [51], including double superfluidity [52,53,54,55,56,57,58], phase-separated states and interfaces [59,60,61,62], supersolidity [63,64,65], pairing from induced interactions [66,67,68,69,70,71,72,73], or in mixed dimensions [74,75,76,77]. [78] investigated a two-dimensional spin-imbalanced Fermi gas immersed in a Bose superfluid, leading to an effective long-range attractive interaction between fermions.
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