Recent experiments with ultra-cold atoms have demonstrated the possibility of realizing fermionic superfluids with imbalanced spin populations experimentally. We discuss how these developments have shed new light on a half-century-old open problem in condensed matter physics, and raised new interrogations of their own.
The search for novel phases of quantum coherent matter has been one of the main driving forces in condensed matter physics for many years. The unprecedented experimental sophistication reached recently in ultracold atomic gases has opened new and exciting perspectives in this search. The ability to externally manipulate the interatomic interaction, the capacity to embed atomic clouds in optical lattices or confine them in low dimensions, as well as the possibility to prepare mixtures of atoms with different statistics and/or populations, is presenting an opportunity to realise and explore novel correlated phases of matter. During the lectures I will focus mainly on aspects of condensation and superfluidity phenomena in fermionic systems. Theoretical elements will be discussed together with recent experimental realisations.
Fermionic superfluids continue to be a topic of current interest and debate in condensed matter and sub-nuclear physics. Recent experiments with laser-cooled atomic gas clouds of fermions seek to explore this physics and point out that discrepancies might arise due to different confining geometries. We reported on realistic numerical simulations with up to 100'000 atoms (a number comparable to that in the actual experiments) that shed light into what might be going on in the laboratory realizations.
In recent years, ultracold bosonic and fermionic atom gases in optical lattices have allowed us to realize experimentally phenomena originally predicted or observed in condensed matter physics with unprecedented control and purity. Among others, proposals have been made to demonstrate a key feature of one dimensional (1D) quantum systems, the so-called spin-charge separation, which has been quite elusive in condensed matter systems. However, as we want to discuss in this paper using the time-dependent density-matrix renormalization group (DMRG), beyond a mere demonstration of spin-charge separation cold atom gases will also shed light on previously inaccessible aspects of this phenomenon. Moreover, the previous proposals for experimental realizations will be revisited taking into account the modelling of an external magnetic field.