SEMINAR+WEBINAR ANNOUNCEMENT

SEMINAR+WEBINAR ANNOUNCEMENT

Monday, 24^th of April 2023 at 11:30
UPC campus nord, B4-212 (aula seminari)
https://meet.google.com/whq-mkve-aja

Arthur Christianen

Max Planck Institute of Quantum Optics, Garching, Germany

 “The Bose polaron and the Efimov effect”

Abstract

In ultracold atomic gases, a unique interplay arises between phenomena known from condensed matter, few-body physics and chemistry. A good example is the Bose polaron problem of an atomic impurity in a Bose-Einstein condensate (BEC). On the one hand, the impurity is dressed by excitations from the medium, similar to an electron in a solid. On the other hand, the Efimov effect known from universal few-body physics can cause the impurity to mediate attractive interactions between the bosons from the BEC.  As a result, an interesting competition arises between the impurity-mediated attraction and the background repulsion in the BEC. If the attraction dominates, this leads to a local collapse of the BEC onto the impurity and rapid recombination [1,2]. If instead the repulsion dominates, one finds a smooth crossover from a polaron into a small molecule. In our recent work [3], we achieve a unified understanding of these phenomena by comparing two state-of-the-art variational methods, fully including both the boson-impurity and interboson interactions.  We show that both the instability and the crossover regime can be studied in realistic experiments, paving the way to an increased understanding of mediated interactions in quantum mixtures of ultracold atoms.

[1] A. Christianen, J. I. Cirac, R. Schmidt, Phys. Rev. Lett. 128, 183401 (2022)
[2] A. Christianen, J. I. Cirac, R. Schmidt, Phys. Rev. A 105, 053302 (2022)
[3] A. Christianen, J. I. Cirac, R. Schmidt, in preparation