Seminar organised by TQC
Subject : Dynamics and collective behavior in ultracold neutral matter and plasmas
Speaker: Hugo Terças, Instituto Superior Técnico, Lisboa
In this talk, I will summarize some of the aspects of three different aspects of cold and ultracold matter: cold atomic traps, Bose-Einstein condensates and ultracold plasmas. I will firstly explain why the long-range forces mediated by light have put the physics of magneto-optical traps (MOTs) again into the stage. Multiple scattering of photons in the trap is responsible for the emergence of a Coulomb-like interaction between the atoms, which is the root for different collective features, namely the emergence of a cut-off frequency and a roton minimum in the excitation spectrum, dynamical instabilities and normal modes. Secondly, I will discuss the effects of advection in rotating Bose-Einstein condensates, and how it may open the door for a new collective mode, analogous to the Rossby wave, which is a drift acoustic mode ubiquitous in geophysics. The effects of this drift term is added to the dispersion relation of the usual Tkachenko modes. Finally, I will consider the dynamics of expansion of ultracold neutral (Rydberg) plasmas, by deriving a Thomas-Fermi potential for the electrons. I will conclude the presentation by suggesting the theoretical possibility of observing slow-light in ultracold plasmas, an effect resulting from the combined dielectric response of electrons and two-level Rydberg atoms.
When and where: Thursday, March 23, 2012 at 16.00 h in room N.008, Campus Drie Eiken