Date/Time
Date(s) - 09/11/2005
3:30 pm - 4:30 pm

Title: Bose-Einstein condensates with dipole-dipole interactions: rotons and other instabilities

Speaker: Dr. Duncan O’Dell

Institute: University of Sussex
Department of Physics & Astronomy

Location: ABB 102

Description:

The key novelty of ultra-cold atoms (atoms cooled to temperatures below a micro-Kelvin) is the remarkable degree to which we can control them. This means that what was previously a theorist’s game of studying highly idealized gedanken experiments, in which this or that parameter was tuned to zero or infinity, or the hamiltonian was chosen to have such-and-such a form, can now often be experimentally realized. Thus, in the ten years since the first Bose-Einstein condensate (BEC) was observed in the lab in 1995 we have witnessed the realization and systematic study of vortices and vortex lattices, the superfluid to Mott-insulator transition in an optical lattice, fermionic superfluidity and the BCS-BEC cross-over, and the fermionization of 1D bosons in the Tonks-Girardeau regime, to name but a few.

In this talk I shall focus upon the control of the interatomic interactions using external electromagnetic fields. We shall see that, on top of controlling the sign and magnitude of the interaction via a Feshbach resonance, one can also choose whether it is short-range or long-range by introducing dipole-dipole interactions. These interactions, which are both long-range and anisotropic, have important consequences for the superfluidity of a BEC and can lead to roton-like instabilities reminiscent of the strongly correlated quantum liquid helium II.