Phase diagram of a strongly interacting spin-imbalanced Fermi gas

Olsen, Ben A.; Revelle, Melissa; Fry, Jacob A.; Sheehy, Daniel E.; Hulet, Randall G.

doi:10.1103/physreva.92.063616

Cited by 34 publications

(38 citation statements)

References 71 publications

(147 reference statements)

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“…In a trapped imbalanced Fermi gas at equilibrium, excess spins reside along the edge of the trap [38]. One naive idea is therefore to phase imprint a soliton onto the system and allow for the excess spins to diffuse from the edge of the trap into the core of the soliton.…”

Section: Discussionmentioning

confidence: 99%

Core filling and snaking instability of dark solitons in spin-imbalanced superfluid Fermi gases

Reichl

Mueller

2017

Phys. Rev. A

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We use the time-dependent Bogoliubov de Gennes equations to study dark solitons in threedimensional spin-imbalanced superfluid Fermi gases. We explore how the shape and dynamics of dark solitons are altered by the presence of excess unpaired spins which fill their low-density core. The unpaired particles broaden the solitons and suppress the transverse snake instability. We discuss ways of observing these phenomena in cold atom experiments.

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Section: Discussionmentioning

confidence: 99%

Core filling and snaking instability of dark solitons in spin-imbalanced superfluid Fermi gases

Reichl

Mueller

2017

Phys. Rev. A

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“…The bundle will cross over from an array of independent 1D tubes for small tunneling t, to a 3D system as t is increased [21,22]. We have employed this geometry to determine the crossover value of t for a spin-imbalanced Fermi gas with various interaction strengths and find a striking universality in the crossover location.Trapped Fermi gases with spin-imbalance have been observed to phase separate at low temperatures in both 3D [23][24][25][26][27] …”

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confidence: 99%

“…Trapped Fermi gases with spin-imbalance have been observed to phase separate at low temperatures in both 3D [23][24][25][26][27] …”

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confidence: 99%

1D to 3D Crossover of a Spin-Imbalanced Fermi Gas

Revelle¹,

Fry²,

Olsen³

et al. 2016

Phys. Rev. Lett.

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We have characterized the one-dimensional (1D) to three-dimensional (3D) crossover of a twocomponent spin-imbalanced Fermi gas of 6 Li atoms in a 2D optical lattice by varying the lattice tunneling and the interactions. The gas phase separates, and we detect the phase boundaries using in situ imaging of the inhomogeneous density profiles. The locations of the phases are inverted in 1D as compared to 3D, thus providing a clear signature of the crossover. By scaling the tunneling rate t with respect to the pair binding energy B , we observe a collapse of the data to a universal crossover point at a scaled tunneling value oftc = 0.025(7).PACS numbers: 67.85. Lm, 71.10.Pm, 37.10.Jk, 05.70.Fh Atomic Fermi gases prepared in two hyperfine sublevels realize a quasi-spin-1 /2 system, for which the two states may be denoted as |↑ and |↓ . Spinimbalanced Fermi gases, where the number of spinup atoms, N ↑ , exceeds the number of spin-down atoms, N ↓ , have been studied extensively in recent years, largely motivated by a search for exotic superfluid phases [1][2][3]. One such superfluid, the FuldeFerrell-Larkin-Ovchinnikov (FFLO) phase [4,5], has not been conclusively observed in three dimensions (3D) but is believed to occupy a large portion of the one-dimensional (1D) phase diagram [6,7]. Measurements have confirmed that the 1D phase diagram is consistent with theories exhibiting FFLO [8], but direct evidence for this phase remains elusive. Since the FFLO phase is expected to be more robust to quantum and thermal fluctuations in higher dimensions, attention has focused on the dimensional crossover [9][10][11][12].A crossover between 1D and 3D regimes may be realized by simply varying the confinement aspect ratio [13][14][15][16][17]. A complementary dimensional crossover occurs by varying the tunneling between tubes aligned in an array, as depicted in Fig. 1(a). Such a geometry, which may be achieved using ultracold atoms in an optical lattice, is more analogous to some material systems, such as carbon nanotube bundles [18] and spin-1 /2 magnet chains [19,20]. The bundle will cross over from an array of independent 1D tubes for small tunneling t, to a 3D system as t is increased [21,22]. We have employed this geometry to determine the crossover value of t for a spin-imbalanced Fermi gas with various interaction strengths and find a striking universality in the crossover location.Trapped Fermi gases with spin-imbalance have been observed to phase separate at low temperatures in both 3D [23][24][25][26][27] FIG. 1. (Color online) (a) Schematic of an array of 1Dcoupled tubes formed by a 2D optical lattice. The tunneling rate t between the tubes increases with decreasing optical lattice depth. (b) Schematic of phase separation for a trapped spin-imbalanced Fermi gas in 1D (top) and in 3D (bottom) at zero temperature. In 1D, the central region is an FFLO partially-polarized superfluid (SFP), with balanced superfluid (SF0) wings for small polarization P . In 3D, for P < P 3D c , a central SF0 core is surrounded by an SFP or ...

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“…In the past decade, remarkable progresses have been made in the study of strongly interacting fermions in three-dimensional (3D) Bose-Einstein condensate(BEC)-Bardeen-Cooper-Schrieffer (BCS) crossover [1][2][3][4], including precise measurements of equations of states (EOS) [5][6][7][8], the investigations of magnetic and pairing/depairing phenomena [9][10][11] and polaron [12][13][14][15] in a spin polarized system. In addition, the 2D Fermi gas has also been realized and attracted a lot of attention both experimentally [16][17][18][19][20][21][22][23] and theoretically [24][25][26][27][28].…”

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Universal properties of Fermi gases in one dimension

He¹,

Chen²,

Zhang³

et al. 2016

Phys. Rev. A

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In this Rapid Communication, we investigate the universal properties of a spin-polarized twocomponent Fermi gas in one dimension (1D) using Bethe ansatz. We discuss the quantum phases and phase transitions by obtaining exact results for the equation of state, the contact, the magnetic susceptibility and the contact susceptibility, giving a precise understanding of the 1D analogue of the Bose-Einstein condensation and Bardeen-Cooper-Schrieffer crossover in three dimension (3D) and the associated universal magnetic properties. In particular, we obtain the exact form of the magnetic susceptibility χ ∼ 1/ √ T exp(−∆/T ) at low temperatures, where ∆ is the energy gap and T is the temperature. Moreover, we establish exact upper and lower bounds for the relation between polarization P and the contact C for both repulsive and attractive Fermi gases. Our findings emphasize the role of the pair fluctuations in strongly interacting 1D fermion systems that can shed light on higher dimensions. In the past decade, remarkable progresses have been made in the study of strongly interacting fermions in three-dimensional (3D) Bose-Einstein condensate(BEC)-Bardeen-Cooper-Schrieffer (BCS) crossover [1-4], including precise measurements of equations of states (EOS) [5][6][7][8], the investigations of magnetic and pairing/depairing phenomena [9][10][11] and polaron [12][13][14][15] in a spin polarized system. In addition, the 2D Fermi gas has also been realized and attracted a lot of attention both experimentally [16][17][18][19][20][21][22][23] and theoretically [24][25][26][27][28]. Despite these advances, fundamental questions still remain. In particular, what is the role of pair fluctuations on thermodynamics and transport phenomena, especially in the vicinity of transition temperature at unitarity.Similar questions can be answered in a more affirmative manner in the case of 1D Fermi gases due to the existence of exactly solvable models. Recently, dramatical progresses have been made in the experimental realizations of many exactly solvable models of 1D interacting bosons and fermions [29,30]. One naturally expects to gain deeper insight into the 1D analogue of the 3D BEC-BCS crossover as well as the associated universal thermodynamics from the Bethe ansatz perspective. In fact, the precise equation of state obtained from the thermodynamic Bethe ansatz (TBA) equations [31] not only gives rise to important characteristics of the Tomonaga-Luttinger liquids (TLL) but also * The authors WBH and YYC contributed equally to the calculations in this paper.provides universal laws, such as quantum scalings, dimensionless ratios, Tan's contact and universal relations between macroscopic properties [32][33][34], which could shed new light on many-body phenomena in higher dimensions. However, a complete derivation of the thermodynamics of an arbitrarily polarized gas and the role of pair fluctuation in 1D systems still remain a challenging problem in the field of cold atoms [25,30,35,36].In this Rapid Communication, we show that the TBA equati...

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Phase diagram of a strongly interacting spin-imbalanced Fermi gas

Cited by 34 publications

References 71 publications

Core filling and snaking instability of dark solitons in spin-imbalanced superfluid Fermi gases

Core filling and snaking instability of dark solitons in spin-imbalanced superfluid Fermi gases

1D to 3D Crossover of a Spin-Imbalanced Fermi Gas

Universal properties of Fermi gases in one dimension

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