Polarons, Dressed Molecules, and Itinerant Ferromagnetism in ultracold Fermi gases

TL;DR

This review explores the properties of impurity atoms in ultracold Fermi gases, focusing on polarons, dressed molecules, and itinerant ferromagnetism, providing insights into strongly interacting quantum mixtures and their phase diagrams.

Contribution

It offers a comprehensive overview of the Fermi polaron problem and its application to understanding itinerant ferromagnetism in ultracold gases, using simple theoretical approaches.

Findings

Polaron problem can be modeled with simple diagrammatic and variational methods.

Provides reliable insights into phase diagrams of imbalanced quantum mixtures.

Connects polaron physics to long-standing questions on itinerant ferromagnetism.

Abstract

In this review, we discuss the properties of a few impurity atoms immersed in a gas of ultracold fermions, the so-called Fermi polaron problem. On one side, this many-body system is appealing because it can be described almost exactly with simple diagrammatic and/or variational theoretical approaches. On the other, it provides quantitatively reliable insight into the phase diagram of strongly interacting population imbalanced quantum mixtures. In particular, we show that the polaron problem can be applied to study itinerant ferromagnetism, a long standing problem in quantum mechanics.