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TT: Fachverband Tiefe Temperaturen

TT 24: Symposium “Condensed Matter Phases in Ultracold Atoms”

TT 24.7: Talk

Thursday, March 29, 2007, 12:25–12:50, H20

Vortex Matter in Optical Lattices — •Michiel Snoek — Institut für Theoretische Physik, Universität Frankfurt, Frankfurt am Main, Deutschland

A Bose-Einstein condensate responds to rotation by forming quantized vortices. The quantum fluctuations of these vortices are greatly enhanced by slicing the Bose-Einstein condensate into a stack of two-dimensional pancake-condensates by means of an optical lattice.

A single vortex line in this setup has bosonic fluctuations and is equivalent to a bosonic string. By trapping fermionic atoms in the vortex cores, a superstring can be realized.

Multiple vortex lines order in a Abrikosov lattice. We have investigated the excitations of the vortex lattice; in particular we studied the Bloch bands of the Tkachenko modes. Vortex fluctuations melt the vortex crystal after which higly correlated quantum liquids are formed. Because of the small number of particles in the pancake Bose-Einstein condensates at every site of the optical lattice, finite-size effects and effects of the inhomogeneous density are important. As a result, the melting of the lattice occurs from the outside inwards. We studied the melting of the vortex lattice as a function of rotation frequency, temperature, and strength of the optical lattice.