Dissipation and fluctuations in elongated bosonic Josephson junctions

TL;DR

This paper explores the complex interplay of dissipation and fluctuations in elongated bosonic Josephson junctions, revealing how sound modes influence quantum tunneling dynamics through damping and stochastic effects.

Contribution

It introduces a microscopic model linking Josephson and sound modes, deriving damping and noise characteristics, and analyzing their impact on phase and population dynamics.

Findings

Coupling between Josephson and sound modes causes damping and stochastic behavior.

Thermal and quantum fluctuations influence the Josephson dynamics.

Time evolution shows oscillating thermalization to equilibrium.

Abstract

We investigate the dynamics of bosonic atoms in elongated Josephson junctions. We find that these systems are characterized by an intrinsic coupling between the Josephson mode of macroscopic quantum tunneling and the sound modes. This coupling of Josephson and sound modes gives rise to a damped and stochastic Langevin dynamics for the Josephson degree of freedom. From a microscopic Lagrangian, we deduce and investigate the damping coefficient and the stochastic noise, which includes thermal and quantum fluctuations. Finally, we study the time evolution of relative-phase and population-imbalance fluctuations of the Josephson mode and their oscillating thermalization to equilibrium.