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Dr. Richard Schmidt

Technische Universität München

Monday, November 5th, 2012 at 02:00:00 PM  

Conference room Querzoli - LENS - via Nello Carrara 1 - Sesto Fiorentino (Florence)

Published on-line at 11:15:39 AM on Monday, November 5th, 2012

Efimov physics beyond universality

Efimov effect in three bosons interactions, universal scaling relations and deviations.

The Efimov effect tells us that three bosons interacting via short-range, resonant interactions form an infinite series of three-body bound states (trimers). In my talk I will first review the basics of Efimov physics, then I will proceed to its main topic: the Efimov effect necessitates to introduce an additional three-body parameter (3BP), which dictates the position of the trimers in the energy spectrum. Recent observations (f.e. in the the group of Grimm or Modugno) suggest that this three-body parameter is a almost universal number.

I will shortly explain how this 3BP comes about in field theoretical descriptions and will review our recent results, where we provide an exact solution of the Efimov spectrum in ultracold gases within the standard two-channel model for Feshbach resonances. It is shown that the finite range in the Feshbach coupling makes the introduction of an adjustable three-body parameter obsolete. The solution explains the observed universality of the 3BP for open-channel dominated resonances. There is a continuous crossover to the closed-channel dominated limit, where the scale in the energy level diagram as a function of the inverse scattering length 1/a is set by the intrinsic length r* associated with the Feshbach coupling.

Additionally, our results provide a number of predictions for the deviations from universal scaling relations between energies and scattering lengths that can be tested in future experiments. If time permits, I will also comment on other recent theoretical developments.

For further informations, please contact Prof. Giovanni Modugno.