Superfluid density and Berezinskii-Kosterlitz-Thouless transition of a spin-orbit-coupled Fulde-Ferrell superfluid

Cao, Ye; Liu, Xia-Ji; He, Lianyi; Long, Gui Lu; Hu, Hui

doi:10.1103/physreva.91.023609

Cited by 16 publications

(13 citation statements)

References 88 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, we observe from figures 6(a)-(c) that the transitions between the gapped and gapless states at moderate Zeeman fields and chemical potentials coincide with the prominent minima of D s diff . This is consistent with the findings of [48] where it was shown that the longitudinal component exhibits a clear minimum when the system becomes gapless. However, in figures 6(b), (c) we see the system reaching a gapped region again at large enough μ without such a drastic change of D s diff than at smaller values of μ.…”

Section: Components Of the Superfluid Weightsupporting

confidence: 93%

“…Therefore, by deploying SOC, one is able to stabilize FF phases considerably against thermal phase fluctuations and increase T BKT . This is similar to continuum studies [12,48,49] where it was proposed that FF states could be observed with the aid of SOC. The difference of λ=0 and λ=0.75 is further demonstrated in figure 1(e), where T BKT andq y for both the cases are plotted as a function of h x at h z =0.…”

Section: Phase Diagrams and The Bkt Temperaturesupporting

confidence: 87%

“…In addition to D s diff , in figures 6(a)-(c) we also plot with solid white lines the boundaries of gapped and gapless superfluid phases. Consistent with previous literature [12][13][14]48], we call the system gapless (or nodal) if one or more of the Bogoliubov quasi-hole branches reach the zero-energy in some part of the momentum space, i.e. the quasi-particle excitation energy vanishes for some momenta.…”

Section: Components Of the Superfluid Weightmentioning

confidence: 62%

See 2 more Smart Citations

Superfluid weight and Berezinskii–Kosterlitz–Thouless temperature of spin-imbalanced and spin–orbit-coupled Fulde–Ferrell phases in lattice systems

2018

View full text Add to dashboard Cite

We study the superfluid weight D s and Berezinskii-Kosterlitz-Thouless (BKT) transition temperatures T BKT in case of exotic Fulde-Ferrell (FF) superfluid states in lattice systems. We consider spinimbalanced systems with and without spin-orbit coupling (SOC) accompanied with in-plane Zeeman field. By applying mean-field theory, we derive general equations for D s and T BKT in the presence of SOC and the Zeeman fields for 2D Fermi-Hubbard lattice models, and apply our results to a 2D square lattice. We show that conventional spin-imbalanced FF states without SOC can be observed at finite temperatures and that FF phases are further stabilized against thermal fluctuations by introducing SOC. We also propose how topologically non-trivial SOC-induced FF phases could be identified experimentally by studying the total density profiles. Furthermore, the relative behavior of transverse and longitudinal superfluid weight components and the role of the geometric superfluid contribution are discussed.performed with quasi-one-dimensional population-imbalanced atomic gases have shown to be consistent with the existence of the FFLO state [33] but unambiguous proof is still missing.In addition to conventional spin-imbalanced quantum gas experiments, recently also synthetic SOC and Zeeman fields have been realized in ultracold gas experiments [34][35][36][37][38] which makes it possible to investigate SOC-induced FFLO states as well. As SOC-induced FFLO states have been predicted to be stable in larger parameter regime than conventional spin-imbalanced FFLO phases [10], synthetic SOC could provide a way to realize FFLO experimentally in ultracold gas systems [15].Low dimensionality has been predicted to favor 40]. However, in two and lower dimensional systems thermal phase fluctuations of the Cooper pair wave functions prevent the formation of true superfluid long range order as stated by the Mermin-Wagner theorem [41]. Instead, only quasi-long range order is possible. In two-dimensions, the phase transition from a normal Fermi gas to a superfluid state of quasi-long range order is determined by the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature T BKT [42]. Below T BKT the system is a superfluid and above T BKT superfluidity is lost.In recent years, SOC-induced FFLO phases in two-dimensional systems have gained considerable attention [7,10,13,14,20,21,25]. In these systems it has been argued that SOC accompanied with the in-plane Zeeman field would yield FFLO states. Furthermore, in [13,14] it was predicted that in the presence of the out-of-plane Zeeman field, i.e. spin-imbalance, SOC-induced FFLO states could be topologically non-trivial and support Majorana fermions. Such topological FFLO states are conceptually new and exotic superconductive phases of matter. However, these studies were performed by applying mean-field theories which do not consider the stability of FFLO states against thermal phase fluctuations in terms of the BKT transition. Superfluidity and BKT transition temperatures of BCS phases in spin-...

show abstract

Section: Components Of the Superfluid Weightsupporting

confidence: 93%

Section: Phase Diagrams and The Bkt Temperaturesupporting

confidence: 87%

Section: Components Of the Superfluid Weightmentioning

confidence: 62%

See 1 more Smart Citation

Superfluid weight and Berezinskii–Kosterlitz–Thouless temperature of spin-imbalanced and spin–orbit-coupled Fulde–Ferrell phases in lattice systems

2018

View full text Add to dashboard Cite

show abstract

“…Hence, we assume that fermions pair at opposite momenta, ignoring the possibility of non-uniform superfluid phases [47][48][49][50]. In Eq.…”

Section: B Calculating the Saddle-point Thermodynamic Potentialmentioning

confidence: 99%

Quantum phase transitions and Berezinskii-Kosterlitz-Thouless temperature in a two-dimensional spin-orbit-coupled Fermi gas

2015

View full text Add to dashboard Cite

We study the effect of spin-orbit coupling on both the zero-temperature and non-zero temperature behavior of a two-dimensional (2D) Fermi gas. We include a generic combination of Rashba and Dresselhaus terms into the system Hamiltonian, which allows us to study both the experimentally relevant equal-Rashba-Dresselhaus (ERD) limit and the Rashba-only (RO) limit. At zero temperature, we derive the phase diagram as a function of the two-body binding energy and Zeeman field. In the ERD case, this phase diagram reveals several topologically distinct uniform superfluid phases, classified according to the nodal structure of the quasiparticle excitation energies. Furthermore, we use a momentum dependent SU(2)-rotation to transform the system into a generalized helicity basis, revealing that spin-orbit coupling induces a triplet pairing component of the order parameter. At non-zero temperature, we study the Berezinskii-Kosterlitz-Thouless (BKT) phase transition by including phase fluctuations of the order parameter up to second order. We show that the superfluid density becomes anisotropic due to the presence of spin-orbit coupling (except in the RO case). This leads both to elliptic vortices and antivortices, and to anisotropic sound velocities. The latter prove to be sensitive to quantum phase transitions between topologically distinct phases. We show further that at a fixed non-zero Zeeman field, the BKT critical temperature is increased by the presence of ERD spin-orbit coupling. Subsequently, we demonstrate that the Clogston limit becomes infinite: TBKT remains non-zero at all finite values of the Zeeman field. We conclude by extending the quantum phase transition lines to non-zero temperature, using the nodal structure of the quasiparticle spectrum, thus connecting the BKT critical temperature with the zero-temperature results.

show abstract

“…Mean field theory has been pushed to investigate the finite temperature behavior of spin-orbit coupled imbalanced Fermi gases, as well [194,195]. It was inferred that together with in-plane and out of plane Zeeman field, spin orbit coupling gives rise to BKT transition in two dimensions, both for gapped as well as gapless FF phases [194,195].…”

Section: Imbalance and Spin-orbit Coupling In Fermi Systemsmentioning

confidence: 99%

Imbalanced Fermi systems and exotic superconducting phases

Karmakar¹

2020

Preprint

View full text Add to dashboard Cite

Superfluid density and Berezinskii-Kosterlitz-Thouless transition of a spin-orbit-coupled Fulde-Ferrell superfluid

Cited by 16 publications

References 88 publications

Superfluid weight and Berezinskii–Kosterlitz–Thouless temperature of spin-imbalanced and spin–orbit-coupled Fulde–Ferrell phases in lattice systems

Superfluid weight and Berezinskii–Kosterlitz–Thouless temperature of spin-imbalanced and spin–orbit-coupled Fulde–Ferrell phases in lattice systems

Quantum phase transitions and Berezinskii-Kosterlitz-Thouless temperature in a two-dimensional spin-orbit-coupled Fermi gas

Imbalanced Fermi systems and exotic superconducting phases

Contact Info

Product

Resources

About