In what forms does matter organize itself under the influence of
interaction? This is the fundamental question of many-body physics, which
arises at all length scales: from the dense quark matter present in the
beginning of our Universe, to the atomic nucleus, the electrons inside a
metal, and the inner workings of a neutron star. While strong interactions
between particles do not allow for a simple description of such systems,
samples of ultracold gases act as a "magnifying glass" in the study of
physics of strongly correlated matter. Unlike condensed matter systems,
many-body processes can be probed in real time, in or out of equilibrium
in dilute mixtures of ultracold gases. This line of research has great
potential to shed light on mechanisms responsible for High-Tc
superconductivity and quantum magnetism, by providing a fully controllable
environment in which fundamental models of condensed matter physics can be
tested with the precision of atomic physics.
To realize such a system, we have constructed a new apparatus that allows
cooling four different species of atoms, fermionic 6Li and 40K, and
bosonic 23Na and 41K. Using this system, we have realized a Bose Einstein
condensate of 41K immersed in a Fermi sea of 40K and detected a wide
Feshbach resonance between them. A lifetime exceeding several tens of
milliseconds is measured at resonance for this mixture. Currently, we use
this mixture to study many-body effects on the physics of impurity atom
interacting with its environment. In this talk, I will summarize our
observations and the progress we have made towards understanding the
science of impurity physics.
