Strongly Interacting Quantum Mixtures of Ultracold Atoms

Presented by Peyman Ahmadi 

The importance of quantum mixtures of ultracold atoms as model systems for various studies such as
condensed matter, neutron stars and as a non-relativistic analog of QCD matter has been well known but
only recently has it been vigorously investigated. We have realized such a mixture by constructing a new
experimental apparatus that simultaneously produces quantum degenerate gases of three different atomic
species, namely of bosonic 23Na and fermionic 6Li and 40K. Many Feshbach resonances between different
combinations of atoms have been detected giving access to mixtures with tunable interactions.
The doubly degenerate two species mass imbalanced 40K–6Li Fermi-Fermi mixture holds promise for
the observation of fermionic superfluidity and Cooper pairing between unlike fermions. Furthermore,
strongly interacting Fermi-Fermi mixtures of unlike fermionic species offer the prospect of observing
universal physics in mass imbalanced mixtures, such as universal transport. Imposing speciesdependent
optical potentials on the mixture will allow the study of systems with mixed dimensionality and impurity
physics such as Anderson localization and the interaction of localized impurities with fermionic
superfluids.
Additionally, with our strongly interacting 23Na–40K mixture, formation of fermionic Feshbach
molecules is within reach. In the rovibrational ground state, NaK molecules possess a large permanent
electric dipole moment and are stable against exchange collisions. Our experiment paves the way to create
a Fermi gas of polar molecules with strong dipole-dipole interactions that dominate the many-body physics
of the gas rather than being a small perturbative effect. In this talk I will give a general introduction to the
topic of ultracold atomic mixtures, discuss their preparation techniques and present our recent results on
studying Bose-Fermi and Fermi-Fermi quantum mixtures.