24 May 2012 Repulsive Polarons in Nature

Image by H. Ritsch

ICFO researcher Dr. Pietro Massignan coauthors a paper reporting in Nature the experimental detection of repulsive polarons. The experimental group led by Prof. Rudolf Grimm at IQOQI and University of Innsbruck (Austria), in collaboration with Prof. Georg Bruun from U. Aarhus (Denmark) and ICFO researcher Dr. Pietro Massignan, announces in a Letter to Nature the investigation of quasi-particles in a mixture of ultracold fermionic gases. The research team prepared an ideal Fermi sea doped with just a few impurities, which as a result of strong-interactions yielded the prototypical examples of dressed quasi-particles, the polarons. The article reports a comprehensive investigation of both attractive and repulsive polarons, evidencing their coherence properties and metastability. This study represents a definite step towards the experimental realization of the simplest model for ferromagnetism, a long-sought but still elusive goal since its theoretical proposal by Stoner some 80 years ago.

The paper has been highlighted in Nature News and Views.

The paper Metastability and Coherence of Repulsive Polarons in a Strongly Interacting Fermi Mixture has been published in Nature by Dr. Christoph Kohstall, Dr. Matteo Zaccanti, PhD student Michael Jag, Dr. Andreas Trenkwalder, Dr. Florian Schreck, Prof. Rudolf Grimm, from IQOQI and U. Innsbruck; Prof. Georg Bruun, from U. Aarhus and Dr. Pietro Massignan, research fellow at ICFO in the group led by Prof. Maciej Lewenstein.