Basic research information
The study of ultracold quantum degenerate atomic gases is the main focus of the research in my lab. Since the first creation of a dilute gas Bose-Einstein condensate in 1995 (see [1]), this field of physics has developed into an extremely active and quickly advancing research area. Modern optics and laser technology is one of the key ingredients in this research, making it possible to implement powerful laser cooling techniques [2].
[1] http://nobelprize.org/physics/laureates/2001/index.html
[2] http://nobelprize.org/physics/laureates/1997/index.html
For getting into the quantum
degenerate regime, the phase space density of a gas needs to be increased
by about twenty orders of magnitude. The first step along this way is
laser cooling. With the help of dissipative light forces a cloud containing
billions of atoms can be cooled down to temperatures of few tens of microK
in just a few seconds. In order to isolate the cloud from the environment
(which remains at room temperature!), the cloud is trapped in the center
of a UHV chamber, being held by magnetic forces.
Similarly, laser cooling can also be used to slow down atoms in an atomic
beam - from velocities of intially above 1000 m/s to a standstill over
a distance of few tens of cm, producing decelerations on the order of
a million times the gravitational acceleration on earth.
Despite its apparent power, laser cooling has got its limitations. In particular, laser cooling loses its effectiveness at temperatures of a few microK, but for creating quantum degenerate gases temperatures in the nK regime are required.Therefore the laser cooling stage needs to be followed by an evaporative cooling stage. During this phase of the experiment the hottest atoms are allowed to escape from the trap, and the remaining ones rethermalize at a lower temperature - similarly to the hot coffee in the picture on the right that cools by evaporating the hottest atoms.
Making a Bose-Einstein condensate or a degenerate Fermi gas typically takes about a minute. The quantum degenerate gases then have a lifetime that is also on the order of many seconds to few minutes, depending mostly on the quality of the vacuum. This is plenty of time to explore the odd behaviour of quantum mechanics. The picture on the left shows one example, namely a vortex lattice in a rapidly rotating BEC. The picture was taken in the group of Eric Cornell at JILA/University of Colorado [3] where it worked before joining the faculty at WSU. By going to extreme rotation rates, mean-field quantum Hall physics has been studied with these rotating BECs. Quite generally, BECs and DFGs can serve as well-controlled model systems for complex condensed matter problems. Here at WSU a new ultracold quantum gas experiment is currently under construction in my lab.
[3] http://jilawww.colorado.edu/bec/
