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 K or 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.
Keywords
Cite
@article{arxiv.1705.04830,
title = {Realizing Fulde-Ferrell Superfluids via a Dark-State Control of Feshbach Resonances},
author = {Lianyi He and Hui Hu and Xia-Ji Liu},
journal= {arXiv preprint arXiv:1705.04830},
year = {2018}
}
Comments
Published version, typos in Supplemental Material corrected