Trojan quasiparticles

TL;DR

This paper demonstrates that a driven bosonic Josephson junction can support stable, collective quasiparticle modes called 'flotons' that resemble Trojan wave packets, with potential implications for mean-field approximations in quantum many-body systems.

Contribution

It introduces and analyzes 'flotons', stable collective modes in a driven bosonic Josephson junction, linking quantum $N$-particle dynamics with mean-field descriptions using Floquet-Mathieu approximation.

Findings

'Flotons' are stable, non-spreading collective modes analogous to Trojan wave packets.

These modes are well described by a Floquet-Mathieu approximation.

Nonheating Trojan modes follow a mean-field description, unlike chaotic modes.

Abstract

We argue that a time-periodically driven bosonic Josephson junction supports stable, quasi-particle-like collective response modes which are $N$-particle analogs of the nonspreading Trojan wave packets known from microwave-driven Rydberg atoms. Similar to their single-particle counterparts, these collective modes, dubbed "flotons", are well described by a Floquet-Mathieu approximation, and possess a well-defined discrete set of excitations. In contrast to other, "chaotic" modes of response, the nonheating Trojan modes conform to a mean-field description, and thus may be of particular interest for the more general question under which conditions the reduction of quantum $N$-particle dynamics to a strongly simplified mean-field evolution is feasible. Our reasoning is supported by phase-space portraits which reveal the degree of correspondence beween the $N$-particle dynamics und the mean-field picture in an intuitive manner.