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

Local energy density functional for superfluid Fermi gases from effective field theory

Antoine Boulet, Gabriel Wlazłowski, Piotr Magierski

Over the past two decades, many studies in the density functional theory context revealed new aspects and properties of strongly correlated superfluid quantum systems in numerous configurations that can be simulated in experiments. This was made possible by the generalization of the local density approximation to superfluid systems by Bulgac [Phys. Rev. C 65, 051305(R) (2002); Phys. Rev. A 76, 040502(R) (2007)]. In the present work, we propose an extension of the superfluid local density approximation, systematically improvable and applicable to a large range of many-body quantum problems getting rid of the fitting procedures of the functional parameters. It turns out that only the knowledge of the density dependence of the quasiparticle properties, namely, the chemical potential, the effective mass, and the pairing gap function, are enough to obtain an explicit and accurate local functional of the densities without any adjustment a posteriori. This opens the way toward an effective field theory formulation of the density functional theory in the sense that we obtain a universal expansion of the functional parameters entering in the theory as a series in pairing gap function. Finally, we discuss possible applications of the developed approach allowing precise analysis of experimental observations. In that context, we focus our applications on the static structure properties of superfluid vortices.Over the past two decades, many studies in the density functional theory context revealed new aspects and properties of strongly correlated superfluid quantum systems in numerous configurations that can be simulated in experiments. This was made possible by the generalization of the local density approximation to superfluid systems by Bulgac [Phys. Rev. C 65, 051305(R) (2002); Phys. Rev. A 76, 040502(R) (2007)]. In the present work, we propose an extension of the superfluid local density approximation, systematically improvable and applicable to a large range of many-body quantum problems getting rid of the fitting procedures of the functional parameters. It turns out that only the knowledge of the density dependence of the quasiparticle properties, namely, the chemical potential, the effective mass, and the pairing gap function, are enough to obtain an explicit and accurate local functional of the densities without any adjustment a posteriori. This opens the way toward an effective field theory formulation of the density functional theory in the sense that we obtain a universal expansion of the functional parameters entering in the theory as a series in pairing gap function. Finally, we discuss possible applications of the developed approach allowing precise analysis of experimental observations. In that context, we focus our applications on the static structure properties of superfluid vortices.

arXiv:2201.07626Physical Review AJul 7, 202210 citations

Theory of Superfluidity

F.W. Cummings, James R. Johnston

Physical ReviewDec 5, 19671 citation

Fermion Cooper pairing with unequal masses: Standard field theory approach

Lianyi He, Meng Jin, Pengfei Zhuang

Fermion Cooper pairing with unequal masses is investigated in a standard field theory approach. We derived the superfluid density and Meissner mass squared of the U(1) gauge field in a general two-species model and found that the often used proportional relation between the two quantities is broken when the fermion masses are unequal. In the weak-coupling region, the superfluid density is always negative but the Meissner mass squared becomes mostly positive when the mass ratio between the pairing fermions is large enough. We established a proper momentum configuration of the LOFF pairing with unequal masses and showed that the LOFF state is energetically favored due to the negative superfluid density. The single-plane-wave LOFF state is physically equivalent to an anisotropic state with a spontaneously generated superflow. The extension to a finite-range interaction is briefly discussed.Fermion Cooper pairing with unequal masses is investigated in a standard field theory approach. We derived the superfluid density and Meissner mass squared of the U(1) gauge field in a general two-species model and found that the often used proportional relation between the two quantities is broken when the fermion masses are unequal. In the weak-coupling region, the superfluid density is always negative but the Meissner mass squared becomes mostly positive when the mass ratio between the pairing fermions is large enough. We established a proper momentum configuration of the LOFF pairing with unequal masses and showed that the LOFF state is energetically favored due to the negative superfluid density. The single-plane-wave LOFF state is physically equivalent to an anisotropic state with a spontaneously generated superflow. The extension to a finite-range interaction is briefly discussed.

arXiv:cond-mat/0604137Physical Review BJul 24, 200625 citations

On the statistical theory of superfluidity

Pierre M. V. Résibois, I. Prigogine

PhysicaJan 1, 19627 citations

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.