Dipolar bosons in one dimension: The case of longitudinal dipole alignment

Abstract

We study by quantum Monte Carlo simulations the low-temperature phase diagram of dipolar bosons confined to one dimension, with dipole moments aligned along the direction of particle motion. A hard core repulsive potential of varying range (σ) is added to the dipolar interactio n, in order to ensure stability of the system against collapse. In the σ → 0 limit the physics of the system is dominated by the potential energy and the ground state is quasi-crystalline; as σ is increased the attractive part of the interaction weakens and the equilibrium phase evolves from quasi-crystalline to a non-superfluid liquid. At a critical value σc, the kinetic energy becomes dominant and the system undergoes a quantum phase transition from a self-bound liquid to a gas. In the gaseous phase with σ → σc, at low density attractive interactions bring the system into a "weak" superfluid regime. However, gas-liquid coexistence also occurs, as a result of which the topologically protected superfluid regime is not approached. arXiv:1911.05216v2 [cond-mat.stat-mech]

Morphology of dipolar Bose droplets

“…Experience accumulated over decades of theoretical studies of clusters of helium and parahydrogen suggests that the most important physical properties (e.g., aspect ratio, binding energy, superfluidity) of a self-bound, free standing cluster of few hundred particles are not significantly different from those of a cluster with one or two orders of magnitude more particle. For example, the binding threshold found here for a cluster of N = 400 particles, namely σ ∼ 0.5, is likely to be very close to the saturation (bulk) value, for which no theoretical estimate has yet been obtained, as the threshold to binding in one dimension for the bulk phase has been determined [36] to be σ ∼ 0.65, and binding is generally weakened in higher dimensions.…”

Polarization angle dependence of the breathing modes in confined one-dimensional dipolar bosons

“…θ = 0, on increasing |a 1D | the g Q1D (θ) in Eq. ( 13) becomes rapidly small and negative, and the key issue is to what extent the system of dipolar gas is still stable against possible collapse [44], the formation of a solitonic/droplets phase [35] or a gas/droplet coexistence [45]. The predictions for the breathing modes are qualitatively different from the repulsive case, since both the VBA and the estimates with A = 3.6, with or without correction to the first order, predict that for Λ > 2 the breathing mode rapidly decreases to reach a minimum with ω 2 b /ω 2 0 < 3, after which it rapidly increases until the overall effective interaction becomes negative.…”