Complex Quantum Systems/Condensed Matter Seminar

Prof. Marios Tsatsos, Sao Carlos Institute of Physics, Sao Paulo University, Brazil

"Bose-Einstein condensates beyond the mean-field approach: principles and applications in ultracold atomic gases"

12:30pm, RLM 11.204

Abstract: Bose-Einstein condensation, theoretically known to appear at ultralow temperatures since the 1920s, was achieved in the laboratory only 20 years ago, in dilute bosonic gases at temperatures close to absolute zero. The wide range of applications and controlability of the system parameters has made them unprecedented tools for exploring novel quantum phases and behaviour. The most common theoretical method employed to tackle these complex systems, typically consisting of tens of thousands of interacting particles is the celebrated mean-field Gross-Pitaevskii model. Even though it has been proven successful in describing various types of nonlinear excitations it does not take into consideration fragmentation and correlations that can develop in time. I will briefly present a systematic theory, the MultiConfigurational Time-Dependet Hartree for Bosons (MCTDHB) [1] that has been developed in order to solve the many-body Schroedinger equation beyond the mean-field approach and can be in principle exact, and the latest numerical implementation (solver) that is freely distributed in the web [2]. I will then discuss some particular applications in Bose gases possessing angular momentum and interacting vortices and discuss the novel concept of phantom vortices. The latter are topological defects in rotating gases that evade detection in the density of the gas but give their signature in the correlation function. Last I will sketch (near-)future applications of our theory and solver that go beyond the field of ultracold bosons and extend to known condensed-matter systems.