Realizing Fulde-Ferrell Superfluids via a Dark-State Control of Feshbach Resonances

Abstract

We propose that the long-sought Fulde-Ferrell superfluidity with nonzero momentum pairing can be realized in ultracold two-component Fermi gases of ${}^{40}$K or ${}^6$Li atoms by optically tuning their magnetic Feshbach resonances via the creation of a closed-channel dark state with a Doppler-shifted Stark effect. In this scheme, two counterpropagating optical fields are applied to couple two molecular states in the closed channel to an excited molecular state, leading to a significant violation of Galilean invariance in the dark-state regime and hence to the possibility of Fulde-Ferrell superfluidity. We develop a field theoretical formulation for both two-body and many-body problems and predict that the Fulde-Ferrell state has remarkable properties, such as anisotropic single-particle dispersion relation, suppressed superfluid density at zero temperature, anisotropic sound velocity and rotonic collective mode. The latter two features can be experimentally probed using Bragg spectroscopy, providing a smoking-gun proof of Fulde-Ferrell superfluidity.

Published version, typos in Supplemental Material corrected

References in corpus (19)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Degenerate Quantum Gases with Spin-Orbit Coupling
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• Resonantly-paired fermionic superfluids
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• BEC-BCS crossover, phase transitions and phase separation in polarized resonantly-paired superfluids
• Bragg spectroscopy of a strongly interacting Fermi gas
• Unconventional superfluid in a two-dimensional Fermi gas with anisotropic spin-orbit coupling and Zeeman fields
• Pairing fluctuations and the superfluid density through the BCS-BEC crossover
• Finite temperature phase diagram of a polarized Fermi gas in an optical lattice
• Finite-Momentum Dimer Bound State in Spin-Orbit Coupled Fermi Gas
• Spectral signatures of the Fulde-Ferrell-Larkin-Ovchinnikov order parameter in one-dimensional optical lattices
• Probing the FFLO phase by double occupancy modulation spectroscopy
• Three-component Ultracold Fermi Gases with Spin-Orbit Coupling
• Resonant enhancement of the FFLO-state in 3D by a one-dimensional optical potential
• Center-of-mass-momentum-dependent interaction between ultracold atoms
• Competition between the Fulde-Ferrell-Larkin-Ovchinnikov phase and the BCS phase in the presence of an optical potential

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• Universal relations and normal-state properties of a Fermi gas with laser-dressed mixed-partial-wave interactions
• Cavity-induced Fulde-Ferrell-Larkin-Ovchinnikov superfluids of ultracold Fermi gases
• Fulde-Ferrell superfluids in spinless ultracold Fermi gases
• Large-momentun tail of one-dimensional Fermi gases with spin-orbit coupling
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• Implementing Majorana fermions in a cold-atom honeycomb lattice with textured pairings
• Engineering nonequilibrium superconducting phases in a voltage-driven superconductor under an external magnetic field
• Superfluid density reduction and spin-imbalanced pairing in a fermionic superfluid due to dynamical boson exchange
• Synthesis of Majorana mass terms in low-energy quantum systems
• Anomalous isothermal compressibility in spin-orbit coupled degenerate Fermi gases