Many-body processes in black and grey matter-wave solitons

TL;DR

This study investigates the quantum many-body dynamics of black and grey matter-wave solitons in a one-dimensional ultracold bosonic system, revealing how quantum fluctuations and correlations influence soliton stability and decay.

Contribution

It introduces an optimized density-engineering method for initializing grey solitons and applies a advanced multi-configurational approach to analyze their many-body decay mechanisms.

Findings

Quantum fluctuations reduce soliton lifetime with increasing velocity.

Decay involves a two-stage process linked to orbital asymmetry.

Localized two-body correlations emerge and decay during soliton evolution.

Abstract

We perform a comparative beyond mean-field study of black and grey solitonic excitations in a finite ensemble of ultracold bosons confined to a one-dimensional box. An optimized density-engineering potential is developed and employed together with phase-imprinting to cleanly initialize grey solitons. Based on our recently developed Multi-Layer Multi-Configuration Time-Dependent Hartree Method for Bosons, we demonstrate an enhancement of the quantum fluctuations limited lifetime of the soliton contrast with increasing soliton velocity. A natural orbital analysis reveals a two-stage process underlying the decay of the soliton contrast. The broken parity symmetry of grey solitons results in a local asymmetry of the orbital mainly responsible for the decay, which leads to a characteristic asymmetry of remarkably localized two-body correlations. The emergence and decay of these correlations as well as their displacement from the instantaneous soliton position are analysed in detail. Finally, the role of phase-imprinting for the many-body dynamics is illuminated and additional non-local correlations in pairs of counter-propagating grey solitons are unravelled.