title: Polarons, dressed molecules and itinerant ferromagnetism in ultracold Fermi gases.
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 hand, 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 a 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 the study of itinerant ferromagnetism, a long-standing problem in quantum mechanics.
authors.affiliation: ICFO-Institut de Ciències Fotòniques, Mediterranean Technology Park, E-08860 Castelldefels, Barcelona, Spain.
authors.forename: Pietro
authors.initials: P
authors.lastname: Massignan
authors.forename: Matteo
authors.initials: M
authors.lastname: Zaccanti
authors.forename: Georg M
authors.initials: GM
authors.lastname: Bruun