Dissipation in mesoscale superfluids

Abstract

We investigate the maximum speed at which a driven superfluid can flow through a narrow constriction with a size on the order of the healing length. Considering dissipation via the thermal nucleation of quantized vortices, we calculate the critical velocity for superfluid 4 He and ultracold atomtronic circuits, identify fundamental length and velocity scales, and are thus able to present results obtained in widely different temperature and density ranges in a universal framework. For ultra-narrow channels we predict a drastic reduction in the critical velocity as the energy barrier for flow reducing thermally activated phase slip fluctuations is suppressed.

Absence of Superfluidity in 2D Dipolar Bose Striped Crystals

“…[24] of, e.g., power-law decay of n(r) at long distance in the striped crystal phase, much less estimates of the condensate fraction of, e.g, ∼ 10 −3 with a claimed relative precision of 10%, made using either PIGS or DMC are not at all believable, especially if accompanied by estimates of the superfluid fraction unphysically close to unity, for a system breaking translational invariance. It is worth mentioning the numerous past predictions of superfluidity of various Bose systems, made using ground state techniques, which were subsequently proven incorrect [48,49,50,51,52,53]. Indeed, finite temperature techniques are now widely regarded as a far superior option for investigating the ground state of Bose systems (for an extensive discussion of this subject, see for instance Ref.…”

Search for superfluidity in supercooled liquid parahydrogen

“…For example, first principle computer simulations based on realistic intermolecular potentials yield evidence of superfluid behavior at low temperature (T = 1 K) of nanoscale size clusters of p-H 2 comprising N 20 molecules [8][9][10][11], a claim for which some experimental confirmation has been obtained [12][13][14]. Moreover, the strong tendency of the system to form a crystal at low temperature, even in confinement [15,16] or in reduced dimensions [17,18], greatly reduces the region of parameter space wherein even a metastable fluid phase may exist.…”

Adsorption of parahydrogen on graphene

“…There is now a wealth of theoretical results showing that the early prediction of bulk p-H 2 superfluidity is incorrect, as it fails to take into account the strong tendency of the system to crystallize at temperatures where Bose condensation and superfluidity ought to take place in a fluid. Crystallization is predicted to occur even in confinement [16,17] and/or in disorder [18][19][20] or reduced dimensions [21,22]. Indeed, first principle computer simulations based on realistic intermolecular potentials yield evidence of superfluidity at low temperature (T ∼ 1 K) only in nanoscale size clusters of p-H 2 comprising fewer than N ∼ 20 molecules [23][24][25][26][27].…”