Particle creation in the spin modes of a dynamically oscillating two-component Bose-Einstein condensate

TL;DR

This paper explores how dynamical changes in a two-component Bose-Einstein condensate can lead to the creation of particles in spin modes, with theoretical and numerical analysis highlighting conditions for observable effects.

Contribution

It introduces a theoretical model for quantum dynamics of spin excitations in a trapped condensate with time-dependent parameters and compares it with numerical simulations.

Findings

Particle creation signatures are weak in expanding condensates.

Resonance conditions enhance particle creation in oscillating condensates.

Theoretical predictions align with numerical simulations for inhomogeneous configurations.

Abstract

We investigate the parametric amplification of the zero-point fluctuations in the spin modes of a two-component Bose-Einstein condensate, triggered by the dynamical evolution of the condensate density. We first make use of a Thomas-Fermi approximation to develop a tractable theoretical model of the quantum dynamics of the Bogoliubov excitations in a harmonically trapped condensate with a time-dependent trapping frequency. The predictions of this model are then compared to an ab-initio numerical study of the correlation functions of density and spin fluctuations for general spatially inhomogeneous configurations. Results are shown for the two cases of expanding and oscillating condensates: while the quantum excitation of spin modes remains weak and relatively featureless in the case of an expanding condensate, clear and experimentally promising signatures of particle creation are anticipated for the oscillating case under suitable resonance conditions between the density and the spin modes.