Unconventional interaction between vortices in a polarized Fermi gas

Abstract

Recently, a homogeneous superfluid state with a single gapless Fermi surface was predicted to be the ground state of an ultracold Fermi gas with spin population imbalance in the regime of molecular Bose-Einstein condensation. We study vortices in this novel state using a symmetry-based effective field theory, which captures the low-energy physics of gapless fermions and superfluid phase fluctuations. This theory is applicable to all spin-imbalanced ultracold Fermi gases in the superfluid regime, regardless of whether the original fermion pairing interaction is weak or strong. We find a remarkable, unconventional form of the interaction between vortices. The presence of gapless fermions gives rise to a spatially oscillating potential, akin to the RKKY indirect-exchange interaction in non-magnetic metals. We compare the parameters of the effective theory to the experimentally measurable quantities and further discuss the conditions for the verification of the predicted new feature. Our study opens up an interesting question as to the nature of the vortex lattice resulting from the competition between the usual repulsive logarithmic (2D Coulomb) and predominantly attractive fermion-induced interactions.

47 pages, 9 figures, accepted by Annals of Physics. See arXiv:cond-mat/0611295 for short version

References in corpus (7)

• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Weakly bound dimers of fermionic atoms
• General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
• Phase diagram of a cold polarized Fermi gas
• Nonequilibrium dynamics and thermodynamics of a degenerate Fermi gas across a Feshbach resonance
• Effective theory of excitations in a Feshbach resonant superfluid