Many-body physics of ultracold gas mixtures with large mass difference

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This project is based on interspecies Feshbach resonances in mixtures of lithium and rubidium atoms which have recently been discovered in our group. With these resonances it will be possible to create strongly correlated many body quantum systems of bosonic and fermionic atoms with large mass ratio. The large mass difference of the constituents (fermionic 6Li, bosonic 7Li, and bosonic 87Rb) is the unique feature of our experiment. It will allow us to realize scenarios in which fermionic lithium generates a Born-Oppenheimer type interaction potential between bosonic rubidium atoms. A prominent signature of such an interaction is the existence of heteronuclear Efimov states, which has been predicted recently. These bound states result from attractive forces between two heavy (rubidium) atoms via an exchange of one light (lithium) atom. Similar to its recently observed homonuclear counterpart, the energy spectrum of such a novel heteronuclear three-body quantum compound is also expected to obey universal scaling laws. Their experimental verification is strongly facilitated in mixtures with large mass ratios as given in our experiment. A second consequence of lithium-induced Born-Oppenheimer forces between rubidium atoms is the formation of “gaseous solids”, i.e. crystalline structures in a dilute gas reminiscent of metallic binding in a solid. They are expected to emerge from mixtures prestructured in a 3D optical lattice. Within this project we also plan to address further topics of fundamental many-body physics such as heteronuclear Tonks gases and Luttinger liquids with 6Li-87Rb fermion-boson and 7Li-87Rb boson-boson mixtures. With our improved apparatus these systems should be well accessible.Our project aims at stringent tests of fundamental models in many-body physics. In general, the experimental realization of such models currently pursued in many groups around the world may turn out as the most important long term result of ultracold atomic physics. Our particular atomic mixture readdresses fundamental questions in condensed matter and solid state physics from the angle of large mass differences and may thus significantly contribute to their solution.