Unconventional Spin Density Waves in Dipolar Fermi Gases

Abstract

The conventional spin density wave (SDW) phase (Overhauser, 1962), as found in antiferromagnetic metal for example (Fawcett 1988), can be described as a condensate of particle-hole pairs with zero angular momentum, $\ell =0$, analogous to a condensate of particle-particle pairs in conventional superconductors. While many unconventional superconductors with Cooper pairs of finite $\ell$ have been discovered, their counterparts, density waves with non-zero angular momenta, have only been hypothesized in two-dimensional electron systems (Nayak, 2000). Using an unbiased functional renormalization group analysis, we here show that spin-triplet particle-hole condensates with $\ell =1$ emerge generically in dipolar Fermi gases of atoms (Lu, Burdick, and Lev, 2012) or molecules (Ospelkaus et al., 2008; Wu et al.) on optical lattice. The order parameter of these exotic SDWs is a vector quantity in spin space, and, moreover, is defined on lattice bonds rather than on lattice sites. We determine the rich quantum phase diagram of dipolar fermions at half-filling as a function of the dipolar orientation, and discuss how these SDWs arise amidst competition with superfluid and charge density wave phases.

arXiv comment5 pages, 3 figures

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• Quantum phases of quadrupolar Fermi gases in coupled one-dimensional systems
• Density-wave steady-state phase of dissipative ultracold fermions with nearest-neighbor interactions
• Competing many-body instabilities in two-dimensional dipolar Fermi gases
• Triplet Superfluidity on a triangular ladder with dipolar fermions
• Local gauge symmetry on optical lattices?
• Itinerant ferromagnetism of a dipolar Fermi gas with Raman-induced spin-orbit coupling
• Pairing from repulsion in a two-dimensional Fermi gas with soft-core interactions
• Weak three-dimensional mediators of two-dimensional triplet pairing
• d_{xy}-Density wave in fermion-fermion cold atom mixtures