Dilute atomic gases have become a powerful tool for studying many-body quantum mechanics. The best example of this is the achievement of Bose-Einstein condensation in 1995 in a gas of Bose atoms, a discovery which has invoked a confluence of ideas from condensed matter, atomic and nuclear physics. Now a concerted research effort is focused on creating and studying a BCS (Bardin-Cooper-Schrieffer) superfluid of Cooper pairs in an atomic Fermi gas. An outstanding issue is the apparent lack of a ‘smoking gun’ for superfluidity in a Fermi gas, since the bulk properties are essentially unaffected by the pairing. We propose to focus on the macroscopic coherence of the gas in the superfluid phase, in particular its ability to sustain quantized vortices. The creation and subsequent detection of such persistent topological features would provide an unambiguous signature of superfluidity in the system.

In the work presented here we investigate the structure and thermodynamic properties of a singly quantized vortex line in a gas of superfluid fermionic atoms. By solving the Bogoliubov-de Gennes equations self-consistently we make the first quantitative determination of the critical rotation frequency for thermodynamic stability of the vortex state, and study the nature of the bound states in the vortex core. These excitations fill the core, making direct imaging of the vortex unlikely. Instead, we propose an experiment to indirectly probe the supercurrent associated with the vortex state with laser fields, in a scheme analogous to Scanning Tunneling Microscopy. Furthermore, it is shown that the vortex state causes a shift of the superfluid transition temperature, which can be understood as a finite size effect.
 
 
 
 
 
 

Nicolai Nygaard

Electron and Optical Physics Division

Physics Laboratory

B105 Building 245

Mailstop 8410

Phone: (301) 975-3748

Fax: (301) 208-6937

Email: nicolai.nygaard@nist.gov

Category: Physics