3,758 research outputs found
Correlations in Ultracold Trapped Few-Boson Systems: Transition from Condensation to Fermionization
We study the correlation properties of the ground states of few ultracold
bosons, trapped in double wells of varying barrier height in one dimension.
Extending previous results on the signature of the transition from a
Bose-condensed state via fragmentation to the hard-core limit, we provide a
deeper understanding of that transition by relating it to the loss of coherence
in the one-body density matrix and to the emerging long-range tail in the
momentum spectrum. These are accounted for in detail by discussing the natural
orbitals and their occupations. Our discussion is complemented by an analysis
of the two-body correlation function.Comment: 22 pages, 7 figure
Excitations of Few-Boson Systems in 1-D Harmonic and Double Wells
We examine the lowest excitations of one-dimensional few-boson systems
trapped in double wells of variable barrier height. Based on a numerically
exact multi-configurational method, we follow the whole pathway from the
non-interacting to the fermionization limit. It is shown how, in a purely
harmonic trap, the initially equidistant, degenerate levels are split up due to
interactions, but merge again for strong enough coupling. In a double well, the
low-lying spectrum is largely rearranged in the course of fermionization,
exhibiting level adhesion and (anti-)crossings. The evolution of the underlying
states is explained in analogy to the ground-state behavior. Our discussion is
complemented by illuminating the crossover from a single to a double well.Comment: 11 pages, 10 figure
Quantum dynamics of two bosons in an anharmonic trap: Collective vs internal excitations
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.Comment: 8 pages, 7 figure
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