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arXiv:2403.19191 · Physical Review A

Superfluid oscillator circuit with a quantum current regulator

Yang Xue, Wen-Kai Bai, Jiao Chen, Wu‐Ming Liu, Jun-Hui Zheng, Tao Yang

Published Apr 15, 2024• 1 citation
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Abstract

We examine the properties of the atomic current in a superfluid oscillating circuit consisting of a mesoscopic channel that connects two reservoirs of a Bose-Einstein condensate. We investigate the presence of a critical current in the channel and examine how the amplitude of the oscillations in the number imbalance between the two reservoirs varies with the system parameters. In addition to highlighting that the dissipative resistance stems from the formation of vortex pairs, we also illustrate the role of these vortex pairs as a quantum current regulator. The dissipation strength is discrete based on the number imbalance, which corresponds to the emergence of vortex pairs in the system. Our findings indicate that the circuit demonstrates characteristics of both voltage-limiting and current-limiting mechanisms. To model the damping behavior of the atomic superfluid circuit, we develop an equivalent LC oscillator circuit with a quantum current regulator.

DOI
10.1103/physreva.109.043312

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We examine the properties of the atomic current in a superfluid oscillating circuit consisting of a mesoscopic channel that connects two reservoirs of a Bose-Einstein condensate. We investigate the presence of a critical current in the channel and examine how the amplitude of the oscillations in the number imbalance between the two reservoirs varies with the system parameters. In addition to highlighting that the dissipative resistance stems from the formation of vortex pairs, we also illustrate the role of these vortex pairs as a quantum current regulator. The dissipation strength is discrete based on the number imbalance, which corresponds to the emergence of vortex pairs in the system. Our findings indicate that the circuit demonstrates characteristics of both voltage-limiting and current-limiting mechanisms. To model the damping behavior of the atomic superfluid circuit, we develop an equivalent LC oscillator circuit with a quantum current regulator.
We have experimentally measured transport of superfluid, bosonic atoms in a mesoscopic system: a small channel connecting two large reservoirs. Starting far from equilibrium (superfluid in a single reservoir), we observe first resistive flow transitioning at a critical current into superflow, characterized by oscillations. We reproduce this full evolution with a simple electronic circuit model. We compare our fitted conductance to two different microscopic phenomenological models. We also show that the oscillations are consistent with LC oscillations as estimated by the kinetic inductance and effective capacitance in our system. Our experiment provides an attractive platform to begin to probe the mesoscopic transport properties of a dilute, superfluid, Bose gas.
We study the onset of dissipation in an atomic Josephson junction between Fermi superfluids in the molecular Bose-Einstein condensation limit of strong attraction. Our simulations identify the critical population imbalance and the maximum Josephson current delimiting dissipationless and dissipative transport, in quantitative agreement with recent experiments. We unambiguously link dissipation to vortex ring nucleation and dynamics, demonstrating that quantum phase slips are responsible for the observed resistive current. Our work directly connects microscopic features with macroscopic dissipative transport, providing a comprehensive description of vortex ring dynamics in three-dimensional inhomogeneous constricted superfluids at zero and finite temperatures.
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We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.
A space-dependent atomic superfluid current with an explicit analytical expression and its role in Bose–Einstein condensates are studied. The factors determining the intensity and oscillating amplitude of the space-dependent atomic superfluid current are explored in detail. Research findings reveal that the intensity of the current can be regulated by setting an appropriate configuration of the trap and its oscillating amplitude can be adjusted via Feshbach resonance. It is numerically demonstrated that the space-dependent atomic superfluid current can exert great influence on the spatial distribution of condensed atoms, and even force condensed atoms into very complex distributional states with spatial chaos.
A space-dependent atomic superfluid current with an explicit analytical expression and its role in Bose–Einstein condensates are studied. The factors determining the intensity and oscillating amplitude of the space-dependent atomic superfluid current are explored in detail. Research findings reveal that the intensity of the current can be regulated by setting an appropriate configuration of the trap and its oscillating amplitude can be adjusted via Feshbach resonance. It is numerically demonstrated that the space-dependent atomic superfluid current can exert great influence on the spatial distribution of condensed atoms, and even force condensed atoms into very complex distributional states with spatial chaos.