Research

The experiments in the Wright group involve cooling a small, dilute gas of lithium atoms down to less than a millionth of a degree above absolute zero. Lithium has two isotopes, one with an odd number of constituent particles (Li-6), and one with an even number (Li-7). This subtle difference becomes extremely important at low temperatures. The isotope Li-6 is a “composite Fermion” and can behave in a manner very much like an electron does in a superconductor.  The work we are doing should help address important problems for many fields of physics, including condensed matter, nuclear, high-energy, and astrophysics. Insights gained through these explorations will facilitate new approaches for predicting the behavior of quantum materials, potentially enabling technological developments in power distribution, sensor technologies, and both classical and quantum computing.

 

 

Recent Posts

Persistent Currents in a Molecular BEC of Fermions

We have just shown that we can clearly distinguish between a ring with a persistent current flowing around it and a stationary superfluid (molecular BEC of Li-6). The basic procedure is to relax the radial confinement of the atoms in the ring trap in a prescribed way, then suddenly release the atoms completely and allow the cloud to expand for several milliseconds. If there is (quantized) circulation around the ring then we see a hole in the middle of the expanded cloud, because of the phase singularity that must be present in the superfluid.

For comparison, if there is no circulation in the superfluid, then the expanded cloud looks like this:

Detecting the vortex signature in this expanding fermionic superfluid is a little more challenging to do well than in previous experiments with atomic Bose condensates (of e.g. rubidium or sodium). The cloud expands quite rapidly even for small numbers of atoms, because the momentum of the atoms is comparatively high due to degeneracy pressure. We’ve got a handle on this, though and it’s clearly not going to be an obstacle to the experiments we have planned. The images above mostly look noisy due to photon shot noise, and we expect to be able to du much better than this soon.

 

  1. Stirring Beam Installed Comments Off on Stirring Beam Installed
  2. Fermionic Atoms in Ring Lattices Comments Off on Fermionic Atoms in Ring Lattices
  3. Fermionic Lithium in a Ring Trap Comments Off on Fermionic Lithium in a Ring Trap
  4. Evaporation in the “Sheet” Trap Comments Off on Evaporation in the “Sheet” Trap