Condensed Matter Seminar: Macroscopic coherent dressing of Bose polarons

Nils Guenther (ICFO)
A single impurity immersed in a dilute Bose-Einstein condensate (BEC) is a remarkably complicated system despite its conceptual simplicity, especially when inter-species interaction is strong.

March 03, 2020

Nils Guenther (ICFO)
Online Seminar
Mon 03. March 2020, 11:30 am (MEZ)

Abstract:

A single impurity immersed in a dilute Bose-Einstein condensate (BEC) is a remarkably complicated system despite its conceptual simplicity, especially when inter-species interaction is strong. In this work, we focus on the case of very weak intra-bosonic repulsion and strong impurity-Boson attraction, which potentially leads to a macroscopic dressing cloud of the impurity.
We start by demonstrating analytically that the particular case of an infinitely-massive impurity interacting with an ideal BEC leads to a bosonic analogue of the Anderson orthogonality catastrophe, i.e., to a ground state which is fully orthogonal to the non-interacting one. Motivated by this, we develop a variational coherent ansatz describing a mobile impurity macroscopicly dressed by the condensate.
The model displays a striking two-parameter universality in terms of the scattering length and the effective range of the bath-impurity potential, and resulting quasi particle properties are in remarkable agreement with available experimental and QMC data.

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