Study of Zero Temperature Ground State Properties of the Repulsive Bose-Einstein Condensate in an Anharmonic Trap

Abstract

The zero-temperature ground state properties of experimental 87Rb condensate are studied in a harmonic plus quartic trap [ V(r) = ½mω2r2 + λr4 ]. The anharmonic parameter (λ) is slowly tuned from harmonic to anharmonic. For each choice of λ, the many-particle Schrödinger equation is solved using the potential harmonic expansion method and determines the lowest effective many-body potential. We utilize the correlated two-body basis function, which keeps all possible two-body correlations. The use of van der Waals interaction gives realistic pictures. We calculate kinetic energy, trapping potential energy, interaction energy, and total ground state energy of the condensate in this confining potential, modelled experimentally. The motivation of the present study is to investigate the crucial dependency of the properties of an interacting quantum many-body system on λ. The average size of the condensate has also been calculated to observe how the stability of repulsive condensate depends on anharmonicity. In particular, our calculation presents a clear physical picture of the repulsive condensate in an anharmonic trap.

Anharmonicity-induced phase transition of spin–orbit coupled Bose–Einstein condensates

“…Before the realization of the SO coupled BECs, the influence of weakly deviated pure harmonic potential (hereafter called anharmonicity) on the properties of condensates (both the ground state [13,[23][24][25][26][27][28][29][30][31][32] and the dynamic properties [22,[33][34][35][36][37][38][39][40][41][42][43]) has been extensively studied, and it is found that the anharmonicity of trapping potential affects one-component condensates [26-29, 33-37, 39, 40], dipolar condensates [38] and rotating condensates [23,24,30]. For one-component condensates, the anharmonicity not only makes condensates with a positive scattering length become metastable condensates [44], but also modifies the frequency of collective oscillations such as dipole and breathing modes [33-35, 37, 39, 40, 45].…”