Sudip Kumar Haldar, Pankaj Debnath, Barnali Chakrabarti
We study the stability of attractive atomic Bose-Einstein condensate in the
anharmonic trap using a correlated many-body method. The anharmonic parameter
($\lambda$) is slowly tuned from harmonic to weak and then to strong
anharmonicity. For each choice of $\lambda$ the many-body equation is solved
adiabatically. The use of the van der Waals interaction gives realistic picture
which substantially differs from the mean-field results. For weak
anharmonicity, we observe that the attractive condensate gains stability with
larger number of bosons compared to that in the pure harmonic trap. The
transition from resonances to bound states with weak anharmonicity also differs
significantly from the earlier study of Moiseyev {\it et.al.}[J. Phys. B: At.
Mol. Opt. Phys. {\bf{37}}, L193 (2004)]. We also study the tunneling of the
metastable condensate very close to the critical number $N_{cr}$ of collapse.
For intermediate anharmonicity, we observe dual tunneling through the two
adjacent barriers. We also calculate the critical value of $\lambda$ where the
left-sided transmission coefficient $T_{left}$ and the right-sided transmission
coefficient $T_{right}$ become equal. This is very special feature which has
not been observed in earlier calculation. For strong anharmonicity we see sharp
decrease in the stability of the condensate. We observe two separate branches
in the stability diagram where we plot $N_{cr}$ with tuned $\lambda$.
View original:
http://arxiv.org/abs/1202.5143
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