Oscillatory pairing amplitude and magnetic compressible-incompressible transitions in imbalanced fermionic superfluids in optical lattices of elongated tubes

Sun, Kuei; Bolech, C. J.

doi:10.1103/physreva.85.051607

Cited by 31 publications

(38 citation statements)

References 29 publications

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“…In particular, dark solitons have recently been experimentally observed in strongly interacting spin balanced Fermi gases [14], where the Cooper pairing wave-function has a phase jump across the soliton [15][16][17][18][19][20][21]. However, dark solitons in the presence of a large spin imbalance have not been well explored.With a large spin imbalance, the ground state of the superfluid is theoretically predicted to be the spatially non-uniform Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase [22] with finite momentum pairing in 1D and quasi-1D [23][24][25][26][27][28], which is partially verified by the experiment [29]. This spatially non-uniform phase does not support dark soliton excitations that usually occur in BCS-type uniform superfluids.…”

mentioning

confidence: 91%

“…With a large spin imbalance, the ground state of the superfluid is theoretically predicted to be the spatially non-uniform Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase [22] with finite momentum pairing in 1D and quasi-1D [23][24][25][26][27][28], which is partially verified by the experiment [29]. This spatially non-uniform phase does not support dark soliton excitations that usually occur in BCS-type uniform superfluids.…”

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confidence: 91%

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Dark Solitons with Majorana Fermions in Spin-Orbit-Coupled Fermi Gases

Mao

et al. 2014

Phys. Rev. Lett.

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We show that a single dark soliton can exist in a spin-orbit-coupled Fermi gas with a high spin imbalance, where spin-orbit coupling favors uniform superfluids over non-uniform Fulde-FerrellLarkin-Ovchinnikov states, leading to dark soliton excitations in highly imbalanced gases. Above a critical spin imbalance, two topological Majorana fermions (MFs) without interactions can coexist inside a dark soliton, paving a way for manipulating MFs through controlling solitons. At the topological transition point, the atom density contrast across the soliton suddenly vanishes, suggesting a signature for identifying topological solitons. Solitons, topological defects arising from the interplay between dispersion and nonlinearity of underlying systems, are significant for many different physical branches [1][2][3][4]. The realization of cold atomic superfluids provides a clean and controllable platform for exploring soliton physics. In cold atomic gases, dark solitons represent quantum excitations of a superfluid with the superfluid order parameter vanishing at the soliton center in conjunction with a phase jump across the soliton. Dark solitons have been extensively investigated in cold atoms [5][6][7][8][9][10][11][12][13]. In particular, dark solitons have recently been experimentally observed in strongly interacting spin balanced Fermi gases [14], where the Cooper pairing wave-function has a phase jump across the soliton [15][16][17][18][19][20][21]. However, dark solitons in the presence of a large spin imbalance have not been well explored.With a large spin imbalance, the ground state of the superfluid is theoretically predicted to be the spatially non-uniform Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase [22] with finite momentum pairing in 1D and quasi-1D [23][24][25][26][27][28], which is partially verified by the experiment [29]. This spatially non-uniform phase does not support dark soliton excitations that usually occur in BCS-type uniform superfluids. On the other hand, uniform superfluids can exist in large spin imbalanced Fermi gases [30] in the presence of spin-orbit (SO) coupling. Since SO coupling for cold atoms has been experimentally generated recently for both bosons and fermions [31][32][33][34][35][36], a natural question is whether such SO coupled superfluids with large spin imbalances can also support dark solitons.More interestingly, it is well known that defects (vortices, edges, etc.) in SO coupled fermionic superfluids with large spin imbalances can accommodate Majorana fermions (MFs) [37][38][39][40][41][42] In this Letter, we address these two important questions by studying dark solitons in degenerate Fermi gases (DFGs) trapped in 1D harmonic potentials with the experimentally already realized SO coupling and spin imbalances. Here the spin imbalance is equivalent to a Zeeman field. In the absence of SO coupling, the FFLO state [22] with an oscillating order parameter amplitude is the ground state [24] with a large Zeeman field, which cannot support dark solitons. With SO coupling, we find (i...

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confidence: 91%

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confidence: 91%

Dark Solitons with Majorana Fermions in Spin-Orbit-Coupled Fermi Gases

Mao

et al. 2014

Phys. Rev. Lett.

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“…If the imbalanced superfluid phase of 1D fermion gases posseses FFLO-type pairing correlations (as indicated * Electronic address: sheehy@lsu.edu theoretically [11][12][13][14][15][16]), and if the LDA holds (so that the uniform case phase diagram is relevant for a trapped gas), then trapped 1D imbalanced Fermi gases may provide the best opportunity to observe signatures of the FFLO state.…”

Section: Introductionmentioning

confidence: 99%

Pairing correlations in a trapped one-dimensional Fermi gas

2015

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We use a BCS-type variational wavefunction to study attractively-interacting quasi onedimensional (1D) fermionic atomic gases, motivated by cold-atom experiments that access the 1D regime using an anisotropic harmonic trapping potential (with trapping frequencies ωx = ωy ωz) that confines the gas to a cigar-shaped geometry. To handle the presence of the trap along the zdirection, we construct our variational wavefunction from the harmonic oscillator Hermite functions that are the eigenstates of the single-particle problem. Using an analytic determination of the effective interaction among harmonic oscillator states along with a numerical solution of the resulting variational equations, we make specific experimental predictions for how pairing correlations would be revealed in experimental probes like the local density and the momentum correlation function.

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“…After the completion of this work, we became aware of recent papers that investigated imbalanced fermionic superfluids in arrays of 1D tubes, allowing inter-tube tunneling [51,52]. They found that the evolution of the physical properties between 1D and 3D (including the inverted phase profiles) can be well described the at a MF level.…”

Section: Discussionmentioning

confidence: 99%

Nesting and lifetime effects in the FFLO state of quasi-one-dimensional imbalanced Fermi gases

Caldas¹,

Continentino²

2013

J. Phys. B: At. Mol. Opt. Phys.

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Abstract.Motivated by the recent experimental realization of a candidate to the Fulde-Ferrell (FF) and the Larkin-Ovchinnikov (LO) states in one dimensional (1D) atomic Fermi gases, we study the quantum phase transitions in these enigmatic, finite momentumpaired superfluids. We focus on the FF state and investigate the effects of the induced interaction on the stability of the FFLO phase in homogeneous spin-imbalanced quasi-1D Fermi gases at zero temperature. When this is taken into account we find a direct transition from the fully polarized to the FFLO state in agreement with exact solutions. Also, we consider the effect of a finite lifetime of the quasi-particles states in the normalsuperfluid instability. In the limit of long lifetimes, the lifetime effect is irrelevant and the transition is directly from the fully polarized to the FFLO state. We show, however, that for sufficiently short lifetimes there is a quantum critical point (QCP), at a finite value of the mismatch of the Fermi wave-vectors of the different quasi-particles, that we fully characterize. In this case the transition is from the FFLO phase to a normal partially polarized state with increasing mismatch. Nesting and Lifetime Effects

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Oscillatory pairing amplitude and magnetic compressible-incompressible transitions in imbalanced fermionic superfluids in optical lattices of elongated tubes

Cited by 31 publications

References 29 publications

Dark Solitons with Majorana Fermions in Spin-Orbit-Coupled Fermi Gases

Dark Solitons with Majorana Fermions in Spin-Orbit-Coupled Fermi Gases

Pairing correlations in a trapped one-dimensional Fermi gas

Nesting and lifetime effects in the FFLO state of quasi-one-dimensional imbalanced Fermi gases

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