Quantum dynamics of two bosons in an anharmonic trap: Collective vs internal excitations

TL;DR

This paper investigates how anharmonic traps influence the quantum dynamics of two interacting bosons, highlighting the coupling between collective and internal excitations and their effects on system behavior.

Contribution

It introduces a detailed analysis of the coupling effects between center of mass and relative motion in an anharmonic trap for two bosons, revealing new dynamical phenomena.

Findings

Strong localization in the relative coordinate at ground state

Collapse of collective oscillations explained by few-mode models

Interplay between collective and internal dynamics observed

Abstract

This work deals with the effects of an anharmonic trap on an interacting two-boson system in one dimension. Our primary focus is on the role of the induced coupling between the center of mass and the relative motion as both anharmonicity and the (repulsive) interaction strength are varied. The ground state reveals a strong localization in the relative coordinate, counteracting the tendency to fragment for stronger repulsion. To explore the quantum dynamics, we study the system's response upon (i) exciting the harmonic ground state by continuously switching on an additional anharmonicity, and (ii) displacing the center of mass, this way triggering collective oscillations. The interplay between collective and internal dynamics materializes in the collapse of oscillations, which are explained in terms of few-mode models.