Orbital Josephson effect and interactions in driven atom condensates on a ring

TL;DR

This paper investigates a novel Josephson effect in ac-driven bosonic condensates on a ring, revealing complex dynamics including Rabi oscillations, self-trapping, chaos, and significant quantum fluctuations.

Contribution

It develops a method to analyze long-term dynamics of driven interacting many-body systems and uncovers how interactions induce effective attraction affecting the Josephson effect.

Findings

Identification of a new Josephson effect in driven bosonic systems

Discovery of diverse dynamical regimes including chaos and self-trapping

Observation of large quantum fluctuations beyond mean-field predictions

Abstract

In a system of ac-driven condensed bosons we study a new type of Josephson effect occurring between states sharing the same region of space and the same internal atom structure. We first develop a technique to calculate the long time dynamics of a driven interacting many-body system. For resonant frequencies, this dynamics can be shown to derive from an effective time-independent Hamiltonian which is expressed in terms of standard creation and annihilation operators. Within the subspace of resonant states, and if the undriven states are plane waves, a locally repulsive interaction between bosons translates into an effective attraction. We apply the method to study the effect of interactions on the coherent ratchet current of an asymmetrically driven boson system. We find a wealth of dynamical regimes which includes Rabi oscillations, self-trapping, and chaotic behavior. In the latter case, a full many-body calculation deviates from the mean-field results by predicting large quantum fluctuations of the relative particle number.