9 research outputs found
Velocity-dependent quantum phase slips in 1D atomic superfluids
Quantum phase slips are the primary excitations in one-dimensional
superfluids and superconductors at low temperatures but their existence in
ultracold quantum gases has not been demonstrated yet. We now study
experimentally the nucleation rate of phase slips in one-dimensional
superfluids realized with ultracold quantum gases, owing along a periodic
potential. We observe a crossover between a regime of temperature-dependent
dissipation at small velocity and interaction and a second regime of
velocity-dependent dissipation at larger velocity and interaction. This
behavior is consistent with the predicted crossover from thermally-assisted
quantum phase slips to purely quantum phase slips.Comment: 7 pages, 6 figure
Observation of a disordered bosonic insulator from weak to strong interactions
We employ ultracold atoms with controllable disorder and interaction to study
the paradigmatic problem of disordered bosons in the full disorder-interaction
plane. Combining measurements of coherence, transport and excitation spectra,
we get evidence of an insulating regime extending from weak to strong
interaction and surrounding a superfluid-like regime, in general agreement with
the theory. For strong interaction, we reveal the presence of a
strongly-correlated Bose glass coexisting with a Mott insulator
Finite-temperature effects on interacting bosonic one-dimensional systems in disordered lattices
14 pages, 19 figuresInternational audienceWe analyze the finite-temperature effects on the phase diagram describing the insulating properties of interacting 1D bosons in a quasi-periodic lattice. We examine thermal effects by comparing experimental results to exact diagonalization for small-sized systems and to density-matrix renormalization group (DMRG) computations. At weak interactions, we find short thermal correlation lengths, indicating a substantial impact of temperature on the system coherence. Conversely, at strong interactions, the obtained thermal correlation lengths are significantly larger than the localization length, and the quantum nature of the T=0 Bose glass phase is preserved up to a crossover temperature that depends on the disorder strength. Furthermore, in the absence of disorder, we show how quasi-exact finite-T DMRG computations, compared to experimental results, can be employed to estimate the temperature, which is not directly accessible in the experiment