3 years ago

High-momentum tail and universal relations of a Fermi gas near a Raman-dressed Feshbach resonance.

Wei Yi, Fang Qin, Guang-Can Guo, Jianwen Jie

In a recent proposal [Jie and Zhang, Phys. Rev. A 95, 060701(R) (2017)], it has been shown that center-of-mass-momentum-dependent two-body interactions can be generated and tuned by Raman-coupling the closed-channel bound states in a magnetic Feshbach resonance. Here we investigate the universal relations in a three-dimensional Fermi gas near such a laser modulated $s$-wave Feshbach resonance. Using the operator-product expansion approach, we find that, to fully describe the high-momentum tail of the density distribution up to $q^{-6}$ ($q$ is the relative momentum), four center-of-mass-momentum-dependent parameters are required, which we identify as contacts. These contacts appear in various universal relations connecting microscopic and thermodynamic properties. One contact is related to the variation of energy with respect to the scattering length, and determines the leading $q^{-4}$ tail of the high-momentum distribution. Another vector contact appears in the sub-leading $q^{-5}$ tail, which is related to the velocity of closed-channel molecules. The other two contacts emerge in the $q^{-6}$ tail, and are related, respectively, to the variation of energy with respect to the effective range, and to the kinetic energy of closed-channel molecules. Particularly, we find that the $q^{-5}$ tail and part of $q^{-6}$ tail of the momentum distribution show anisotropic features. We derive the universal relations, and, as a concrete example, estimate the contacts for the zero-temperature superfluid ground state of the system using a mean-field approach to verify the anisotropic features in the high-momentum tails of this system.

Publisher URL: http://arxiv.org/abs/1801.07448

DOI: arXiv:1801.07448v2

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