5 research outputs found
Universal vortex formation in rotating traps with bosons and fermions
When a system consisting of many interacting particles is set rotating, it
may form vortices. This is familiar to us from every-day life: you can observe
vortices while stirring your coffee or watching a hurricane. In the world of
quantum mechanics, famous examples of vortices are superconducting films and
rotating bosonic He or fermionic He liquids. Vortices are also observed
in rotating Bose-Einstein condensates in atomic traps and are predicted to
exist for paired fermionic atoms. Here we show that the rotation of trapped
particles with a repulsive interaction leads to a similar vortex formation,
regardless of whether the particles are bosons or (unpaired) fermions. The
exact, quantum mechanical many-particle wave function provides evidence that in
fact, the mechanism of this vortex formation is the same for boson and fermion
systems.Comment: 4 pages, 4 figure
Gyroscopic motion of superfluid trapped atomic condensates
The gyroscopic motion of a trapped Bose gas containing a vortex is studied.
We model the system as a classical top, as a superposition of coherent
hydrodynamic states, by solution of the Bogoliubov equations, and by
integration of the time-dependent Gross-Pitaevskii equation. The frequency
spectrum of Bogoliubov excitations, including quantum frequency shifts, is
calculated and the quantal precession frequency is found to be consistent with
experimental results, though a small discrepancy exists. The superfluid
precession is found to be well described by the classical and hydrodynamic
models. However the frequency shifts and helical oscillations associated with
vortex bending and twisting require a quantal treatment. In gyroscopic
precession, the vortex excitation modes are the dominant features
giving a vortex kink or bend, while the is found to be the dominant
Kelvin wave associated with vortex twisting.Comment: 18 pages, 7 figures, 1 tabl