Condensed Matter Physics Seminar

2 p.m., Thursday, February 23, 2006
Room 1201, Physics Building

 Quantum chaos in Bose-Einstein Condensates

Chaunwei Zhang

(CMTC, University of Maryland)

Abstract:  The realization of Bose-Einstein condensation has opened new opportunities for studying dynamical systems in the presence of many-body interactions. In the talk, I discuss how the interactions between atoms modify quantum dynamics of two textbook paradigms in quantum chaos: quantum kicked rotor and billiards.

A periodically kicked ring of a Bose-Einstein condensate is considered as a nonlinear generalization of the quantum kicked rotor. For weak interactions between atoms, periodic motion (anti-resonance) becomes quasiperiodic (quantum beating) but remains stable. There exists a critical strength of interactions beyond which quasiperiodic motion becomes chaotic, resulting in instability of the condensate manifested by exponential growth in the number of noncondensed atoms. Similar behavior is observed for dynamically localized states (essentially quasiperiodic motions), where stability remains for weak interactions but is destroyed by strong interactions.

We investigate the possibility of quantum (or wave) chaos for the Bogoliubov excitations of a Bose-Einstein condensate in billiards. Because of the mean field interaction in the condensate, the Bogoliubov excitations are very different from the single particle excitations in a non-interacting system. Nevertheless, we predict that the statistical distribution of level spacings is unchanged by mapping the non-Hermitian Bogoliubov operator to a real symmetric matrix. We numerically test our prediction by using a phase shift method for calculating the excitation energies.

Host:  Das Sarma
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