Self-consistent fragmented excited states of trapped condensates

TL;DR

This paper introduces a new class of self-consistent, fragmented excited states in trapped condensates, which are energetically more favorable and stable than traditional Gross-Pitaevskii excited states.

Contribution

The authors develop a generalized mean-field approach revealing a novel class of stable, fragmented excited states with lower energies than standard GP states.

Findings

Fragmented states have lower energies than GP excited states.

These states are stable against particle number and trap shape variations.

A numerical example demonstrates the existence of these states.

Abstract

Self-consistent excited states of condensates are solutions of the Gross-Pitaevskii (GP) equation and have been amply discussed in the literature and related to experiments. By introducing a more general mean-field which includes the GP one as a special case, we find a new class of self-consistent excited states. In these states macroscopic numbers of bosons reside in different one-particle functions, i.e., the states are fragmented. Still, a single chemical potential is associated with the condensate. A numerical example is presented, illustrating that the energies of the new, fragmented, states are much lower than those of the GP excited states, and that they are stable to variations of the particle number and shape of the trap potential.