Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate
Abstract
The problem of an impurity particle moving through a bosonic medium plays a fundamental role in physics. However, the canonical scenario of a mobile impurity immersed in a Bose-Einstein condensate (BEC) has not yet been realized. Here, we use radio frequency spectroscopy of ultracold bosonic K atoms to experimentally demonstrate the existence of a well-defined quasiparticle state of an impurity interacting with a BEC. We measure the energy of the impurity both for attractive and repulsive interactions, and find excellent agreement with theories that incorporate three-body correlations, both in the weak-coupling limits and across unitarity. The spectral response consists of a well-defined quasiparticle peak at weak coupling, while for increasing interaction strength, the spectrum is strongly broadened and becomes dominated by the many-body continuum of excited states. Crucially, no significant effects of three-body decay are observed. Our results open up exciting prospects for studying mobile impurities in a bosonic environment and strongly interacting Bose systems in general.
Keywords
Cite
@article{arxiv.1604.07883,
title = {Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate},
author = {Nils B. Jørgensen and Lars Wacker and Kristoffer T. Skalmstang and Meera M. Parish and Jesper Levinsen and Rasmus S. Christensen and Georg M. Bruun and Jan J. Arlt},
journal= {arXiv preprint arXiv:1604.07883},
year = {2016}
}