Spin-orbit-coupling-induced anharmonic collective modes in a Bose-Einstein condensate

The collective excitations of a spin-orbit-coupled Bose-Einstein condensate are investigated by using a variational method and numerical simulation. The collective modes are depicted in zero-momentum and plane-wave phases, while the mechanism for inducing the anharmonic collective oscillations is re...

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Bibliographic Details
Published in:Europhysics letters 2018-01, Vol.121 (2), p.20003
Main Authors: Yu, Zi-Fa, Xue, Ju-Kui
Format: Article
Language:English
Subjects:
03.75.Kk
03.75.Mn
05.45.-a
Anharmonicity
Atomic interactions
Bose-Einstein condensates
Coupled modes
Excitation
Harmonic oscillation
Orbital mechanics
Oscillation modes
Phase transitions
Plane waves
Spin dynamics
Spin-orbit interactions
Transition points
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Summary:The collective excitations of a spin-orbit-coupled Bose-Einstein condensate are investigated by using a variational method and numerical simulation. The collective modes are depicted in zero-momentum and plane-wave phases, while the mechanism for inducing the anharmonic collective oscillations is revealed analytically. The coupling among spin-orbit coupling, Raman coupling, and atomic interaction results in multiple external collective modes, which can lead to the collective dynamics being the superposition of the multiple harmonic oscillations. When one of the external frequencies is close to the inherent frequency of the conventional condensate and the amplitudes of other external frequencies vanish, the collective oscillations are harmonic, otherwise the collective oscillations are anharmonic. Thus the collective dynamics can undergo a harmonicity-anharmonicity transition. This can provide a possible way for elaborating distinct collective oscillation modes. Moreover, the collective excitations exhibit distinct properties in different phases, while the softening of collective modes is detected at the phase transition point, which can be used to map out the phase boundaries in experiment.
ISSN:0295-5075
1286-4854
DOI:10.1209/0295-5075/121/20003