Pairing in a two-dimensional Fermi gas with population imbalance

Wolak, Mathew; Grémaud, Benoît; Scalettar, Richard; Batrouni, G. G.

doi:10.1103/physreva.86.023630

Cited by 40 publications

(43 citation statements)

References 51 publications

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“…Non-zero-momentum pairing fluctuations are dominant at large polarization and low temperature, which is in accord with the large region found in Ref. [35] where the pair momentum distribution function is peaked at finite momenta. For temperatures T 0.05, the difference is positive at the critical polarization P c (T ) implying that the FFLO instability is reached before the conventional superfluid one in this region of the phase diagram [45].…”

supporting

confidence: 90%

Fulde-Ferrell-Larkin-Ovchinnikov pairing as leading instability on the square lattice

Gukelberger¹,

Lienert²,

Kozik³

et al. 2016

Phys. Rev. B

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We study attractively interacting spin-1 2 fermions on the square lattice subject to a spin population imbalance. Using unbiased diagrammatic Monte Carlo simulations we find an extended region in the parameter space where the Fermi liquid is unstable towards formation of Cooper pairs with nonzero center-of-mass momentum, known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. In contrast to earlier mean-field and quasi-classical studies we provide quantitative and well-controlled predictions on the existence and location of the relevant Fermi-liquid instabilities. The highest temperature where the FFLO instability can be observed is about half of the superfluid transition temperature in the unpolarized system. PACS numbers: 71.10. Hf,37.10.Jk,74.20.Mn Fifty years after the initial prediction by Fulde, Ferrell, Larkin, and Ovchinnikov (FFLO) [1,2], superconducting phases with spontaneously broken translational invariance are still at the center of interest in such diverse fields as solid state physics, cold atomic gases, nuclear physics, and dense quark matter in neutron stars [3][4][5][6][7]. While the underlying mechanism is generic enough to apply to any partially polarized Fermi system, it has proven surprisingly difficult to unambiguously observe such phases in nature. Recently, however, experimental evidence has been mounting for their existence in heavy fermion compounds [8][9][10] and layered organic materials [11][12][13][14][15]. On the other hand, experiments with ultracold atoms, which are among the cleanest imbalanced Fermi systems without the need for a magnetic field, so far failed to demonstrate inhomogeneous superfluidity [16,17] -although there is some evidence for such a phase in one dimension (1D) [18] -possibly due to small extent of the parameter region where an FFLO phase may exist in three dimensions (3D) and difficulties in reaching sufficiently low temperatures [5].On the theoretical side, results on the existence and nature of FFLO phases based on well-controlled microscopic theories are scarce, with the exception of 1D systems, where exact analytical and numerical studies are possible [19][20][21][22][23][24][25], and where finite-momentum pairing is a generic feature of the spin-imbalanced phase diagram. In higher dimensions, most studies are based on effective field theories in the neighborhood of critical points or resort to quasi-classical or mean-field approximations. For 3D Fermi gases, many features of the mean-field phase diagram [26] have been corroborated by fixed-node diffusion quantum Monte Carlo calculations [27]; whether the FFLO phase does exist in a small sliver of the phase diagram, as predicted by the mean-field theory, is however still subject to debate.The FFLO state is expected [3,4] to occupy a larger parameter region in two dimensions (2D), and lattice effects may further increase its stability [28,29]. Correspondingly, mean-field calculations [30,31] and realspace dynamical mean-field theory (DMFT) for fermions in anisotropic optical lattices find a st...

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supporting

confidence: 90%

Fulde-Ferrell-Larkin-Ovchinnikov pairing as leading instability on the square lattice

Gukelberger¹,

Lienert²,

Kozik³

et al. 2016

Phys. Rev. B

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“…(38). The function f (z) has no zeros inside the unit circle, so to use the Jensen formula we only need f (0).…”

Section: B Case Of ∆ < ∆C1mentioning

confidence: 99%

Fulde-Ferrell-Larkin-Ovchinnikov state of two-dimensional imbalanced Fermi gases

Sheehy

2015

Phys. Rev. A

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The ground-state phase diagram of attractively-interacting Fermi gases in two dimensions with a population imbalance is investigated. We find the regime of stability for the Fulde-Ferrell-LarkinOvchinnikov (FFLO) phase, in which pairing occurs at finite wavevector, and determine the magnitude of the pairing amplitude ∆ and FFLO wavevector q in the ordered phase, finding that ∆ can be of the order of the two-body binding energy. Our results rely on a careful analysis of the zero temperature gap equation for the FFLO state, which possesses nonanalyticities as a function of ∆ and q, invalidating a Ginzburg-Landau expansion in small ∆.

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“…Indeed, on a bipartite lattice, the FFLO state can be mapped into a stripe state via a simple particle-hole transformation [34,35]. In finite size DQMC calculations, one can observe short range stripe order and enhanced susceptibilities [36,37], but, largely due to the fermionic sign problem, a finite size scaling analysis clearly showing a phase transition to a striped state is still out of reach.…”

Section: Introductionmentioning

confidence: 99%

Dynamical mean-field theory study of stripe order and d -wave superconductivity in the two-dimensional Hubbard model

Vanhala

Törmä

2018

Phys. Rev. B

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We use cellular dynamical mean-field theory with extended unit cells to study the ground state of the two-dimensional repulsive Hubbard model at finite doping. We calculate the energy of states where d-wave superconductivity coexists with spatially nonuniform magnetic and charge order and find that they are energetically favored in a large doping region as compared to the uniform solution. We also study the spatial form of the density and the superconducting and magnetic order parameters at different doping values.

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Pairing in a two-dimensional Fermi gas with population imbalance

Cited by 40 publications

References 51 publications

Fulde-Ferrell-Larkin-Ovchinnikov pairing as leading instability on the square lattice

Fulde-Ferrell-Larkin-Ovchinnikov pairing as leading instability on the square lattice

Fulde-Ferrell-Larkin-Ovchinnikov state of two-dimensional imbalanced Fermi gases

Dynamical mean-field theory study of stripe order and d -wave superconductivity in the two-dimensional Hubbard model

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