Superfluidity in the interior-gap states

Wu, Shin-Tza; Yip, Sungkit

doi:10.1103/physreva.67.053603

Cited by 89 publications

(93 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This approach has proved to yield equivalent results as that of Ref. [13]. We then specialize to the case of equal mass fermions and evaluate the superfluid density in the relevant parameter regime for the realization of the BP1 phase.…”

Section: Superfluid Density Calculationmentioning

confidence: 99%

“…The theoretical interest in pairing with mismatched Fermi surfaces has been revitalized by the proposal of breachedpairing superfluidity, with a number of exotic superfluid states being proposed or revisited. [13,14] Breached-pairing superfluid phase with two gapless Fermi surfaces (BP2), related to the unstable Sarma phase, [15] was found to be stable under the introduction of new effects, such as the mass imbalance and/or momentum-dependent pairing interaction. [16,17] Important developments in the subject are recent studies by various groups [18,19,20] investigating the Feshbach-resonant regime of strong interactions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Unconventional interaction between vortices in a polarized Fermi gas

2008

View full text Add to dashboard Cite

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.

show abstract

Section: Superfluid Density Calculationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Unconventional interaction between vortices in a polarized Fermi gas

2008

View full text Add to dashboard Cite

show abstract

“…Superfluidity or superconductivity with mismatched Fermi momenta also appears in other systems, e.g., electronic superconductor in a strong external magnetic field [10,11], asymmetric nuclear matter [12], and in imbalanced cold atomic systems [13,14]. It has been an unsolved old problem how a BCS superconductivity is destroyed as the mismatch is increased and what exotic phases may occur before entering the normal phase.…”

Section: Introductionmentioning

confidence: 99%

“…Obviously, there should be something missing for our understanding of the pairing breaking state if we failed to observe the (LO)FF state in the mismatch regime where the magnetic or superfluid density instability [14,27] develops. In Refs.…”

Section: Introductionmentioning

confidence: 99%

Inhomogeneity driven by Higgs instability in a gapless superconductor

et al. 2007

View full text Add to dashboard Cite

The fluctuations of the Higgs and pseudo Nambu-Goldstone fields in the 2SC phase with mismatched pairing are described in the nonlinear realization framework of the gauged Nambu-JonaLasinio model. In the gapless 2SC phase, not only Nambu-Goldstone currents can be spontaneously generated, but the Higgs field also exhibits instablity. The Nambu-Goldstone currents generation indicates the formation of the single plane wave LOFF state and breaks rotation symmetry, while the Higgs instability favors spatial inhomogeneity and breaks translation invariance. In this paper, we focus on the Higgs instability which has not drawn much attention yet. The Higgs instability cannot be removed without a long range force, thus it persists in the gapless superfluidity and induces phase separation. In the case of g2SC state, the Higgs instability can only be partially removed by the electric Coulomb energy. However, it is not excluded that the Higgs instability might be completely removed in the charge neutral gCFL phase by the color Coulomb energy.

show abstract

“…The former exhibits a chromomagnetic instability [6,7] while the latter a superfluid density instability [8]. Recent studies have demonstrated that this type of instability is related to the local phase fluctuation of the superconducting order parameter, i.e., the Nambu-Goldstone boson fields [9,10,11,12].…”

mentioning

confidence: 99%

Higgs instability in gapless superfluidity/superconductivity

et al. 2007

View full text Add to dashboard Cite

In this letter we explore the Higgs instability in the gapless superfluid/superconducting phase. This is in addition to the (chromo)magnetic instability that is related to the fluctuations of the Nambu-Goldstone bosonic fields. While the latter may induce a single-plane-wave LOFF state, the Higgs instability favors spatial inhomogeneity and cannot be removed without a long range force. In the case of the g2SC state the Higgs instability can only be partially removed by the electric Coulomb energy. But this does not exclude the possibility that it can be completely removed in other exotic states such as the gCFL state. 12.38.Aw, 26.60.+c Superfluidity or superconductivity with mismatched Fermi momenta appears in many systems such as the charge neutral dense quark matter, the asymmetric nuclear matter, and in imbalanced cold atomic gases. The mismatch plays the role of breaking the Cooper pairing. But it is not understood how a BCS superconductor is destroyed as the mismatch is increased. It was proposed in the 1960s that the competition between the pair breaking and the pair condensation would induce an unconventional superconducting phase, the Larkin-OvchinnikovFulde-Ferrel (LOFF) state [1]. Recently it was found that if the mismatch is larger than the gap magnitude, a gapless superconducting phase [2,3] or a breached pairing (BP) [4] can be formed in a charge neutral quark matter or in a constrained imbalanced cold atom system, respectively. Another scenario for the ground state at moderate mismatch is the phase separation[5] between of superfluid/superconducting and normal phases.Both gapless superconducting and BP phases exhibit instabilities. The former exhibits a chromomagnetic instability [6,7] while the latter a superfluid density instability [8]. Recent studies have demonstrated that this type of instability is related to the local phase fluctuation of the superconducting order parameter, i.e., the Nambu-Goldstone boson fields [9,10,11,12]. This type of instability induces the formation of the single-planewave FF-like state [13,14,15,16,17].The imbalanced cold atom systems such as the 40 K and 6 Li offer an intriguing experimental opportunity to understand the pair breaking states. However, recent experiments [18] on these systems did not show explicit evidence of the BP state or the LOFF state, rather they produced strong evidence of the phase separation at moderate mismatch. We explain in this letter that the BP state or the FF state maybe prevented to form there because of the Higgs instability induced by the mismatch. The Higgs instability is related to the magnitude fluctuation of the superconducting order parameter, i.e., the Higgs field. It causes spatial inhomogeneity that may lead to phase separation. The Higgs instability was also considered in [20], where it was named "amplitude instability".The Higgs instability is an inhomogeneous extension of the Sarma instability against a homogeneous variation of the order parameter. Consider a system described by the Hamiltonian H with a spontaneous ...

show abstract

Superfluidity in the interior-gap states

Cited by 89 publications

References 10 publications

Unconventional interaction between vortices in a polarized Fermi gas

Unconventional interaction between vortices in a polarized Fermi gas

Inhomogeneity driven by Higgs instability in a gapless superconductor

Higgs instability in gapless superfluidity/superconductivity

Contact Info

Product

Resources

About