Observation of Anisotropic Superfluid Density in an Artificial Crystal

Tao, J.; Zhao, M.; Spielman, I. B.

doi:10.1103/physrevlett.131.163401

Cited by 10 publications

(9 citation statements)

References 38 publications

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“…This approach involves determining the phase response to moving walls by solving two Poisson-like equations for the vector auxiliary equation (14). From these solutions the superfluid fraction can be evaluated using equation (17). We then applied this using a 2D soft-core model, although we note that our approach immediately extends to the planar dipolar gas, and was used for the results presented in [43].…”

Section: Discussionmentioning

confidence: 99%

“…Similarly the Leggett bounds could also be applied to this case. Since recent experiments have been able to apply the Leggett upper bound to BECs in 1D optical lattices [17,18], we expect this avenue of investigation may be practical for experiments considering superfluidity of higher dimensional supersolids (or artificial supersolids prepared using BECs in higher dimensional optical lattices). This might be complemented by other approaches, e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Thus we see that ϕ 1 (x) describes the response to the quasimomentum phase gradient arising from the crystalline density. In 1D this can lead to the overall phase profile having a staircase pattern (see [17]). Also, the unchanged density profile means that we can set Φ → Φ 0 ≡ ´d2 x ′ U(x − x ′ )|ψ 0 (x ′ )| 2 .…”

Section: Appendix Superfluid Fraction Tensor and Effective Massmentioning

confidence: 99%

“…Recently two groups have quantified the superfluid fraction in an artificial supersolid produced by applying an optical lattice to a BEC [17,18] (i.e. with imposed, rather than spontaneously formed density order).…”

Section: Introductionmentioning

confidence: 99%

“…with imposed, rather than spontaneously formed density order). Their superfluid measurements were based on two methods: (i) a superfluid bound developed by Leggett, which requires the precise measurement of the density profile [18]; and (2) a ratio of the speeds of sound propagating parallel and perpendicular to the lattice used to obtain the effective mass (and thereby the superfluid fraction) along the lattice [17,18]. It is currently not clear how to extend these ideas to two-dimensional (2D) or three-dimensional (3D) supersolids, where the superfluid fraction is properly a rank-2 tensor.…”

Section: Introductionmentioning

confidence: 99%

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Superfluid fraction tensor of a two-dimensional supersolid

Blakie

2024

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

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We investigate the superfluid fraction of crystalline stationary states within the framework of mean-field Gross-Pitaevskii theory. Our primary focus is on a two-dimensional Bose-Einstein condensate with a non-local soft-core interaction, where the superfluid fraction is described by a rank-2 tensor. We then calculate the superfluid fraction tensor for crystalline states exhibiting triangular, square, and stripe geometries across a broad range of interaction parameters. Factors leading to an anisotropic superfluid fraction tensor are also considered. We also refine the Leggett bounds for the superfluid fraction of the 2D system. We systematically compare these bounds to our full numerical results, and other results in the literature. This work is of direct relevance to other supersolid systems of current interest, such as supersolids produced using dipolar Bose-Einstein condensates.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Appendix Superfluid Fraction Tensor and Effective Massmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Superfluid fraction tensor of a two-dimensional supersolid

Blakie

2024

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

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Stabilizing persistent currents in an atomtronic Josephson junction necklace

Pezzè,

Xhani,

Daix

et al. 2024

Nat Commun

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Arrays of Josephson junctions are at the forefront of research on quantum circuitry for quantum computing, simulation, and metrology. They provide a testing bed for exploring a variety of fundamental physical effects where macroscopic phase coherence, nonlinearities, and dissipative mechanisms compete. Here we realize finite-circulation states in an atomtronic Josephson junction necklace, consisting of a tunable array of tunneling links in a ring-shaped superfluid. We study the stability diagram of the atomic flow by tuning both the circulation and the number of junctions. We predict theoretically and demonstrate experimentally that the atomic circuit withstands higher circulations (corresponding to higher critical currents) by increasing the number of Josephson links. The increased stability contrasts with the trend of the superfluid fraction – quantified by Leggett’s criterion – which instead decreases with the number of junctions and the corresponding density depletion. Our results demonstrate atomic superfluids in mesoscopic structured ring potentials as excellent candidates for atomtronics applications, with prospects towards the observation of non-trivial macroscopic superpositions of current states.

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Measurement of the superfluid fraction of a supersolid by Josephson effect

Biagioni,

Antolini,

Donelli

et al. 2024

Nature

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A new class of superfluids and superconductors with spatially periodic modulation of the superfluid density is arising1–12. It might be related to the supersolid phase of matter, in which the spontaneous breaking of gauge and translational symmetries leads to a spatially modulated macroscopic wavefunction13–16. This relation was recognized only in some cases1,2,5–9 and there is the need for a universal property quantifying the differences between supersolids and ordinary matter, such as the superfluid fraction, which measures the reduction in superfluid stiffness resulting from the spatial modulation16–18. The superfluid fraction was introduced long ago16, but it has not yet been assessed experimentally. Here we demonstrate an innovative method to measure the superfluid fraction based on the Josephson effect, a ubiquitous phenomenon associated with the presence of a physical barrier between two superfluids or superconductors19, which might also be expected for supersolids20, owing to the spatial modulation. We demonstrate that individual cells of a supersolid can sustain Josephson oscillations and we show that, from the current–phase dynamics, we can derive directly the superfluid fraction. Our study of a cold-atom dipolar supersolid7 reveals a relatively large sub-unity superfluid fraction that makes realistic the study of previously unknown phenomena such as partially quantized vortices and supercurrents16–18. Our results open a new direction of research that may unify the description of all supersolid-like systems.

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Observation of Anisotropic Superfluid Density in an Artificial Crystal

Cited by 10 publications

References 38 publications

Superfluid fraction tensor of a two-dimensional supersolid

Superfluid fraction tensor of a two-dimensional supersolid

Stabilizing persistent currents in an atomtronic Josephson junction necklace

Measurement of the superfluid fraction of a supersolid by Josephson effect

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