Abstract
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, flowing 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.
Highlights
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
When the temperature is much higher than the free-energy barrier between two metastable states, T ≫ δF/kB, the order parameter may overcome the barrier via thermal fluctuations, causing the formation of thermally activated phase slips (TAPS) with a nucleation rate following the Arrhenius law Γ ∝ e−δF/kBT22,23
In the TAQPS regime G depends on T but not on v, G ~ T2K−3
Summary
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 observe a clear crossover between a temperature-dependent regime and a velocity dependent regime, in general agreement with theoretical predictions for the crossover from thermal to quantum phase slips[16,17,18,19]. This indicates that QPS can be observed and controlled in ultracold quantum gases. When the temperature is much higher than the free-energy barrier between two metastable states, T ≫ δF/kB, the order parameter may overcome the barrier via thermal fluctuations, causing the formation of thermally activated phase slips (TAPS) with a nucleation rate following the Arrhenius law Γ ∝ e−δF/kBT22,23. The analytical form of δF and T∗ depends on the specific type of obstacle experienced by the superflow, e.g
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