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

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.

8 pages, 7 figures

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• Two trapped particles interacting by a finite-ranged two-body potential in two spatial dimensions
• Many-body theory for systems with particle conversion: Extending the multiconfigurational time-dependent Hartree method
• Exact dynamics and decoherence of two cold bosons in a 1D harmonic trap
• Excitations of attractive 1-D bosons: Binding vs. fermionization
• Attractive Bose-Einstein condensates in anharmonic traps: Accurate numerical treatment and the intriguing physics of the variance
• Ground-state correlation properties of charged bosons trapped in strongly anisotropic harmonic potentials