Dynamical instability of a condensate induced by a rotating thermal gas.
We study surface modes of the condensate in the presence of a rotating thermal cloud in an axisymmetric trap. By considering collisions that transfer atoms between the condensate and the noncondensate, we find that m>0 modes, which rotate in the same sense as the thermal cloud, damp less strongly than m<0 modes, where m is the polarity of the excitation. We show that above a critical angular rotation frequency, equivalent to the Landau stability criterion, m>0 modes become dynamically unstable, leading to the possibility of vortex nucleation. We also generalize our stability analysis to treat the case where the stationary state of the condensate already possesses a single vortex.
Williams
J E
JE
Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7.
Zaremba
E
E
Jackson
B
B
Nikuni
T
T
Griffin
A
A