16,623 research outputs found
Surface excitations, shape deformation and the long-time behavior in a stirred Bose-Einstein condensate
The surface excitations, shape deformation and the formation of persistent
current for a Gaussian obstacle potential rotating in an highly oblate
Bose-Einstein condensate(BEC)are investigated. Vortex dipole can be produced
and trapped in the center of the stirrer even for slow motion of the stirring
beam. When the barrier angular velocity is above some critical value, the
condensate shape can be deformed remarkably according to the rotation frequency
due to the existence of plenty of surface wave excitations. After a long enough
time, a few vortices are found to be left either trapped in the condensate or
pinned by the obstacle, a vortex dipole or several vortices can be trapped at
the beam center, which enables the possibility of vortex manipulation.Comment: 5 pages, 4 figure
Edge States and Quantum Hall Effect in Graphene under a Modulated Magnetic Field
Graphene properties can be manipulated by a periodic potential. Based on the
tight-binding model, we study graphene under a one-dimensional (1D) modulated
magnetic field which contains both a uniform and a staggered component. New
chiral current-carrying edge states are generated at the interfaces where the
staggered component changes direction. These edge states lead to an unusual
integer quantum Hall effect (QHE) in graphene, which can be observed
experimentally by a standard four-terminal Hall measurement. When Zeeman spin
splitting is considered, a novel state is predicted where the electron edge
currents with opposite polarization propagate in the opposite directions at one
sample boundary, whereas propagate in the same directions at the other sample
boundary.Comment: 5 pages, 4 figure
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