2017/05/31 by Lianyi He, Hui Hu, Xia-Ji Liu
Physics and Astronomy · #Anisotropy #Atomic and Subatomic Physics Research #Atomic physics #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Fermi gas #Feshbach resonance #Pairing #Physics #Quantum mechanics #Quantum, superfluid, helium dynamics #Superconductivity #Superfluidity #cond-mat.quant-gas #cond-mat.supr-con #nucl-th
paper · pdf · doi:10.1103/physrevlett.120.045302
published as Phys. Rev. Lett. 120, 045302 (2018) · Published version, typos in Supplemental Material corrected
openalex publication_date 2018/01/25 · arxiv created 2018/01/26 · arxiv updated 2018/01/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We propose that the long-sought Fulde-Ferrell superfluidity with nonzero momentum pairing can be realized in ultracold two-component Fermi gases of 40K or 6Li 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.