Vortices in a Highly Rotating Bose Condensed Gas

Superfluids, with their dissipationless flow and exotic topologies, have puzzled
researchers in diverse fields of physics for almost a century. One of the hallmark features
of superfluids is their response to rotation, which requires the fluid to be pierced by an
array quantized singularities or vortices. Over the past few years, vortices and the
lattices they organize into have become one of the major fields of experimental research
with dilute gas Bose-Einstein condensates.

This thesis explores the physics of vortices and vortex lattices in the dilute gas
Bose-Einstein condensate while drawing connections to other superfluid systems. In addition
to characterizing several equilibrium vortex effects, this work also studies several
excitations. By removing atoms from the rotating condensate with a tightly focused,
resonant laser, the density can be locally suppressed, creating aggregate vortices containing
many units of circulation. These so called “giant vortices” offer insight into
the dynamical stability of density defects in this system. Using similar techniques we
can excite and directly image Tkachenko waves in the vortex. These low frequency
modes are a consequence of the small but nonvanishing elastic shear modulus of the
vortex-filled superfluid.

Finally, by working at extremely high rotations we can create a Bose-Einstein condensates
in the lowest Landau level. In this regime, which requires rotation rates greater
than 99% of the centrifugal limit for a harmonically trapped gas, we are able observe
several expected and unexpected shifts in the physical properties of the condensate.
In conclusion the dilute gas Bose-Einstein condensates offers a rich system in
which to study vortex physics, and explore dynamical effects common to all rotating
superfluids.