Ground state fragmentation of repulsive BEC in double-trap potentials

TL;DR

This paper investigates how the ground state of a repulsive Bose-Einstein condensate fragments in double-trap potentials, revealing critical parameters and the influence of trap geometry on fragmentation behavior.

Contribution

It demonstrates the critical conditions for ground state fragmentation in double-trap potentials and how trap geometry controls the number and fraction of fragments, including maximal boson numbers.

Findings

Fragmentation occurs above critical scattering length or boson number.

Trap geometry determines critical parameters for fragmentation.

Maximal boson number for fragmentation can be manipulated by trap design.

Abstract

The fragmentation of the ground state of a repulsive condensate immersed into a double-trap potential is found to be a general and critical phenomenon. It takes place for a given number of bosons if their scattering length is larger than some critical value or for a given value of the scattering length if the number of bosons is above some critical number. We demonstrate that the geometry of the inner trap determines these critical parameters while the number of the fragments and the fraction of bosons in the various fragments can be manipulated by the outer trap. There is also a maximal number of bosons for which the ground state is fragmented. If this number is exceeded, the fragmented state becomes a very low-lying excited state of the condensate. This maximal number of bosons can be substantially manipulated by varying the inner and outer traps. To study three-fold fragmentation we have chosen a potential well with two barriers as the inner trap and embedded by two types of outer ones. A many-fold fragmentation is also addressed.