We show that unconventional spin order arises naturally in two-component dipolar Fermi gases of atoms or molecules, which recently became accessible experimentally, in optical lattices. Using an unbiased functional renormalization-group analysis, we find that dipolar interactions lead to an instability of the gas toward an $\ensuremath{\ell}=1$ spin-density wave state. This phase is the particle-hole analog of spin-triplet, $p$ -wave Cooper pairs. The order parameter for such spin-density waves of $p$ -wave orbital symmetry is a vector 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 on the square lattice as a function of the dipolar orientation and discuss how these exotic spin-density waves emerge amidst competition with superfluid and charge-density wave phases.We show that unconventional spin order arises naturally in two-component dipolar Fermi gases of atoms or molecules, which recently became accessible experimentally, in optical lattices. Using an unbiased functional renormalization-group analysis, we find that dipolar interactions lead to an instability of the gas toward an $\ensuremath{\ell}=1$ spin-density wave state. This phase is the particle-hole analog of spin-triplet, $p$-wave Cooper pairs. The order parameter for such spin-density waves of $p$-wave orbital symmetry is a vector 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 on the square lattice as a function of the dipolar orientation and discuss how these exotic spin-density waves emerge amidst competition with superfluid and charge-density wave phases.

arXiv:1209.2671Physical Review AApr 5, 201316 citations

Spin Waves in Spin-Polarized Quantum Gases

Eugene P. Bashkin

Physical Review LettersSep 23, 198512 citations

Mixing dipolar condensates: a new opportunity for enhancing superfluid pairing in a spin-polarized Fermi gas

Ben Kain, Hong Yuan Ling

The recent experimental progress in realizing Bose-Fermi mixtures and dipolar quantum gases has created the exciting possibility of creating dipolar Bose-Fermi mixtures with intriguing and unique properties. In a dipolar condensate, the dipole-dipole interaction represents a control knob inaccessible to nondipolar Bosons. Thus, mixing dipolar bosons with fermions may open up new possibilities for creating superfluids with unconventional pairings. We consider a mixture of a spin-polarized Fermi gas and a dipolar Bose-Einstein condensate in a three-dimensional setting in which s-wave scattering between fermions and the quasiparticles of the dipolar condensate can result in an effective attractive Fermi-Fermi interaction anisotropic in nature and tunable by the dipolar interaction. We develop a procedure which allows us to determine the parameters such as densities and scattering lengths that are required to achieve optimal critical temperature before the system starts to phase separate. We perform a systematic investigation, finding that a superfluid with a critical temperature, that is orders of magnitude higher than achievable in nondipolar mixtures, can be realized in dipolar mixtures at experimentally accessible densities and scattering lengths before the system phase separates.The recent experimental progress in realizing Bose-Fermi mixtures and dipolar quantum gases has created the exciting possibility of creating dipolar Bose-Fermi mixtures with intriguing and unique properties. In a dipolar condensate, the dipole-dipole interaction represents a control knob inaccessible to nondipolar Bosons. Thus, mixing dipolar bosons with fermions may open up new possibilities for creating superfluids with unconventional pairings. We consider a mixture of a spin-polarized Fermi gas and a dipolar Bose-Einstein condensate in a three-dimensional setting in which s-wave scattering between fermions and the quasiparticles of the dipolar condensate can result in an effective attractive Fermi-Fermi interaction anisotropic in nature and tunable by the dipolar interaction. We develop a procedure which allows us to determine the parameters such as densities and scattering lengths that are required to achieve optimal critical temperature before the system starts to phase separate. We perform a systematic investigation, finding that a superfluid with a critical temperature, that is orders of magnitude higher than achievable in nondipolar mixtures, can be realized in dipolar mixtures at experimentally accessible densities and scattering lengths before the system phase separates.

Journal of Physics Conference SeriesFeb 8, 20130 citations

Reentrant superfluidity and pair density wave in single-component dipolar Fermi gases

Yanming Che, Jibiao Wang, Qijin Chen

We study the superfluidity of single-component dipolar Fermi gases in three dimensions using a pairing fluctuation theory, within the context of BCS-BEC crossover. The transition temperature ${T}_{c}$ for the dominant ${p}_{z}$ wave superfluidity exhibits a remarkable reentrant behavior as a function of the pairing strength induced by the dipole-dipole interaction (DDI), which leads to an anisotropic pair dispersion. The anisotropy and the long-range nature of the DDI cause ${T}_{c}$ to vanish for a narrow range of intermediate interaction strengths, where a pair density wave emerges as the ground state. The superfluid density and thermodynamics below ${T}_{c}$ , along with the density profiles in a harmonic trap, are investigated as well. Implications for experiments are discussed.We study the superfluidity of single-component dipolar Fermi gases in three dimensions using a pairing fluctuation theory, within the context of BCS-BEC crossover. The transition temperature ${T}_{c}$ for the dominant ${p}_{z}$ wave superfluidity exhibits a remarkable reentrant behavior as a function of the pairing strength induced by the dipole-dipole interaction (DDI), which leads to an anisotropic pair dispersion. The anisotropy and the long-range nature of the DDI cause ${T}_{c}$ to vanish for a narrow range of intermediate interaction strengths, where a pair density wave emerges as the ground state. The superfluid density and thermodynamics below ${T}_{c}$, along with the density profiles in a harmonic trap, are investigated as well. Implications for experiments are discussed.

arXiv:1503.04453Physical Review AJun 10, 20169 citations

p

-wave Cooper pairs. The order parameter for such spin-density waves of

p

-wave orbital symmetry is a vector 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 on the square lattice as a function of the dipolar orientation and discuss how these exotic spin-density waves emerge amidst competition with superfluid and charge-density wave phases.

We study the superfluidity of single-component dipolar Fermi gases in three dimensions using a pairing fluctuation theory, within the context of BCS-BEC crossover. The transition temperature

{T}_{c}

for the dominant

{p}_{z}

wave superfluidity exhibits a remarkable reentrant behavior as a function of the pairing strength induced by the dipole-dipole interaction (DDI), which leads to an anisotropic pair dispersion. The anisotropy and the long-range nature of the DDI cause

{T}_{c}

to vanish for a narrow range of intermediate interaction strengths, where a pair density wave emerges as the ground state. The superfluid density and thermodynamics below

{T}_{c}

, along with the density profiles in a harmonic trap, are investigated as well. Implications for experiments are discussed.