Stability Criteria for Breached-Pair Superfluidity

Forbes, Michael McNeil; Gubankova, Elena; Liu, W. Vincent; Wilczek, Frank

doi:10.1103/physrevlett.94.017001

Cited by 171 publications

(215 citation statements)

References 16 publications

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“…It was discovered later on that stable gapless superconductivity could be possible under the constraint of particle number fixing in a non-relativistic model [14] (see also Ref. [15] for more discussions on stability) and of electric and color neutrality in the gapless regime of the 2SC (g2SC) phase [16].…”

Section: Introductionmentioning

confidence: 99%

Analytical and numerical evaluation of the Debye and Meissner masses in dense neutral three-flavor quark matter

Fukushima

2005

Phys. Rev. D

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We calculate the Debye and Meissner masses and investigate chromomagnetic instability associated with the gapless color superconducting phase changing the strange quark mass Ms and the temperature T . Based on the analytical study, we develop a computational procedure to derive the screening masses numerically from curvatures of the thermodynamic potential. When the temperature is zero, from our numerical results for the Meissner masses, we find that instability occurs for A1 and A2 gluons entirely in the gapless color-flavor locked (gCFL) phase, while the Meissner masses are real for A4, A5, A6, and A7 until Ms exceeds a certain value that is larger than the gCFL onset. We then handle mixing between color-diagonal gluons A3, A8, and photon Aγ, and clarify that, among three eigenvalues of the mass squared matrix, one remains positive, one is always zero because of an unbroken U(1)Q symmetry, and one exhibits chromomagnetic instability in the gCFL region. We also examine the temperature effects that bring modifications into the Meissner masses. The instability found at large Ms for A4, A5, A6, and A7 persists at finite T into the u-quark color superconducting (uSC) phase which has u-d and s-u but no d-s quark pairing and also into the two-flavor color superconducting (2SC) phase characterized by u-d quark pairing only. The A1 and A2 instability also goes into the uSC phase, but the 2SC phase has no instability for A1, A2, and A3. We map the unstable region for each gluon onto the phase diagram as a function of Ms and T .

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Section: Introductionmentioning

confidence: 99%

Analytical and numerical evaluation of the Debye and Meissner masses in dense neutral three-flavor quark matter

Fukushima

2005

Phys. Rev. D

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“…[24,25,26,27,28] One of the states commonly found in various theoretical approaches [18,19,20] is a homogeneous superfluid with a single gapless Fermi surface on the molecular (BEC) side of the Feshbach resonance (the BEC regime). This state, which consists of coexisting molecular superfluid and fully-polarized Fermi gas of the majority-spin component, is closely related to the BP2 phase, [16,17] but differs from the latter in the number of gapless Fermi surfaces. We will refer to this phase as BP1 (breached-pairing state with a single gapless Fermi surface) after Ref.…”

Section: Introductionmentioning

confidence: 99%

“…[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. [21] The first experiments on ultracold fermionic gases with spin population imbalance have recently been carried out [22,23] and thereby brought the subject to the forefront of the cold atom physics.…”

Section: Introductionmentioning

confidence: 99%

Unconventional interaction between vortices in a polarized Fermi gas

2008

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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.

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“…The transition between the phases is sharp in the local density approximation (LDA) and local minimization of the grand potential rules out the possibility of the local maxima of the free energy, known as the Sarma [25] or breach-pair (BP) [26] state. LDA approach can, however, be modified to include a possibility for a BP phase if one minimizes the total (global) energy of the system [27].…”

Section: Introductionmentioning

confidence: 99%

Ultracold polarized Fermi gas at intermediate temperatures

Martikainen

2006

Phys. Rev. A

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We consider non-zero temperature properties of the polarized two-component Fermi gas. We point out that stable polarized paired states which are more stable than their phase separated counterparts with unpolarized superfluid region can exist below the critical temperature. We also solve the system behavior in a trap using the local density approximation and find gradually increasing polarization in the center of the system as the temperature is increased. However, in the strongly interacting region the central polarization increases most rapidly close to the mean-field critical temperature, which is known to be substantially higher than the critical temperature for superfluidity. This indicates that most of the phase separation occurs in the fluctuation region prior to superfluidity and that the polarization in the actual superfluid is modest.

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Stability Criteria for Breached-Pair Superfluidity

Cited by 171 publications

References 16 publications

Analytical and numerical evaluation of the Debye and Meissner masses in dense neutral three-flavor quark matter

Analytical and numerical evaluation of the Debye and Meissner masses in dense neutral three-flavor quark matter

Unconventional interaction between vortices in a polarized Fermi gas

Ultracold polarized Fermi gas at intermediate temperatures

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