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Seminar : Alexej Streltsov

par Webmestre - publié le

« A time-dependent tour with novel many-body phenomena in attractive and repulsive Bose-systems »

par Alexej I. Streltsov de l’Université de Heidelberg

Abstract :

The density of the many-particle quantum system is the main observable routinely detected in modern experiments with trapped ultra-cold atomic clouds. Hence, the evolution of quantum many-particle system can be monitored and compared with theoretical (numerical) solutions of the respective many-particle Schrödinger equation governing this dynamics.
In this tour, we look at novel phenomena which can directly be observed and identified in the densities of the evolving many-particle systems and connect them with respective numerical simulations on the many-body level. (
We start our tour from Bose systems with attractive inter-particle interactions supporting “solitonic” solutions – dynamically-stable localized coherent wave-packets propagating without dispersion. We show that together with the “solitons” there are new classes of localized objects which are not coherent, but rather fragmented. As an example we discuss dynamical formations of many-body Schrödinger-cat like states which we have termed “Catons”. The physics behind localized “solitons” in attractive systems is intuitively clear – the inter-particle attraction enforces particles to stay together. But what about repulsive interactions ? Can dynamically-stable localized objects be formed in bosonic systems with repulsive interactions ?

In the second part of our tour we have a look over trapped Bose systems with strong repulsive inter-particle interactions of finite ranges. We emonstrate that the ground state of these systems can indeed be fragmented in localized structures which are very stable dynamically with respects to trong external perturbations. The physics behind is identified and explained.