Spectroscopy of the soliton lattice formation in quasi-one-dimensional fermionic superfluids with population imbalance

Abstract

Motivated by recent experiments in low-dimensional trapped fermionic superfluids, we study a quasi-one-dimensional (quasi-1D) superfluid with a population imbalance between two hyperfine states using an exact mean-field solution for the order parameter. When an effective "magnetic field" exceeds a critical value, the superfluid order parameter develops spatial inhomogeneity in the form of a soliton lattice. The soliton lattice generates a band of quasiparticle states inside the energy gap, which originate from the Andreev bound states localized at the solitons. Emergence of the soliton lattice is accompanied by formation of a spin-density wave, with the majority fermions residing at the points in space where the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) order parameter vanishes. We discuss possibilities for experimental detection of the quasi-1D FFLO state using elastic and inelastic optical Bragg scattering and radio-frequency spectroscopy. We show that these measurements can provide necessary information for unambiguous identification of the spatially-inhomogeneous quasi-1D FFLO state and the soliton lattice formation.

23 pages, 12 figures, minor changes, updated references

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• From Planar Solitons to Vortex Rings and Lines: Cascade of Solitonic Excitations in a Superfluid Fermi Gas
• Long-time behavior of the momentum distribution during the sudden expansion of a spin-imbalanced Fermi gas in one dimension
• Dark Solitons with Majorana Fermions in Spin-Orbit-Coupled Fermi Gases
• Dimer, trimer and FFLO liquids in mass- and spin-imbalanced trapped binary mixtures in one dimension
• Pair tunneling, phase separation and dimensional crossover in imbalanced fermionic superfluids in a coupled array of tubes
• Oscillatory pairing amplitude and magnetic compressible-incompressible transitions in imbalanced fermionic superfluids in optical lattices of elongated tubes
• Moving solitons in a one-dimensional fermionic superfluid
• Non-Fermi liquid at the FFLO quantum critical point
• Ring solitons and soliton sacks in imbalanced fermionic systems
• FFLO strange metal and quantum criticality in two dimensions: theory and application to organic superconductors
• Fluctuations of imbalanced fermionic superfluids in two dimensions induce continuous quantum phase transitions and non-Fermi liquid behavior
• Rotating Fulde-Ferrell-Larkin-Ovchinnikov state in cold Fermi gases
• Enhanced visibility of the Fulde-Ferrell-Larkin-Ovchinnikov state in one dimensional Bose-Fermi mixtures near the immiscibility point
• Collective modes of a soliton train in a Fermi superfluid
• Dimensional Crossover in a Spin-imbalanced Fermi gas
• Signatures of the BCS-BEC crossover in the yrast spectra of Fermi quantum rings
• Proposal for interferometric detection of topological defects in modulated superfluids
• Stability of the Fulde-Ferrell-Larkin-Ovchinnikov states in anisotropic systems and critical behavior at thermal $m$-axial Lifshitz points
• Nesting and lifetime effects in the FFLO state of quasi-one-dimensional imbalanced Fermi gases
• Triplet pair correlations in {\it s-}wave superfluids as a signature of the FFLO state
• Protocol to engineer Fulde-Ferrell-Larkin-Ovchinnikov states in a cold Fermi gas
• Class of variational ansaetze for the "spin-incoherent" ground-state of a Luttinger liquid coupled to a spin bath
• Bose-Hubbard model with occupation-parity couplings
• Anomalous Flux Quantization in the Spin-Imbalanced Attractive Hubbard Ring
• Unconventional pairing in few-fermion systems tuned by external confinement