Trung tâm Vật lý tính toán - Trung tam Vat ly tinh toan

Seminar on Theoretical and Computational Physics:
Title	Beliaev theory of spinor Bose-Einstein condensates
Speaker	Nguyen Thanh Phuc
Affiliation	Physics Department, University of Tokyo
Date	Tuesday, 14-08-2012
Time	10:00 AM
Location	Meeting room on the 1st floor, Institute of Physics, 10 Dao Tan, Ba Dinh, Hanoi
Abstract	By generalizing the Green’s function approach proposed by Beliaev [1, 2], we investigate the effect of quantum depletion on the energy spectra of elementary excitations in an F = 1 spinor Bose-Einstein condensate, in particular, of 87Rb atoms in an external magnetic field. We find that quantum depletion increases the effective mass of magnons in the spin-wave excitations with quadratic dispersion relations. The enhancement factor turns out to be the same for both ferromagnetic and polar phases, and also independent of the magnitude of the external magnetic field. The lifetime of these magnons in a 87Rb spinor BEC is shown to be much longer than that of phonons. We propose an experimental setup to measure the effective mass of these magnons in a spinor Bose gas by exploiting the effect of a nonlinear dispersion relation on the spatial expansion of a wave packet of transverse magnetization. This type of measurement has practical applications, for example, in precision magnetometry. [1] S. T. Beliaev, Soviet Physics JETP 7 (1958) 299. [2] S. T. Beliaev, Soviet Physics JETP 7 (1958) 289.

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