Observation of Heteronuclear Feshbach Resonances in a Mixture of Bosons and Fermions

Abstract

Three magnetic-field induced heteronuclear Feshbach resonances were identified in collisions between bosonic 87Rb and fermionic 40K atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and 543+/-2 G. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding (-281+/-15)a(0) and (-54+/-12)a(0), respectively. The width of the loss feature at 543 G is 3.7+/-1.5 G wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.

Mean-field description of a dynamical collapse of a fermionic condensate in a trapped boson-fermion mixture

“…However, the situation of collapse exploiting a Feshbach resonance in the bosonfermion system is more exciting and controlled experiment could be done by jumping the boson-fermion scattering length a BF as in the collapse experiment with bosonic condensate [11]. This seems possible in 6 Li-23 Na [23] and 40 K-87 Rb [24] systems using the recently discovered Feshbach resonances in these systems. The increase in the number of bosonic atoms in the boson-fermion condensate to initiate the collapse is a slow stochastic process as opposed to sudden controlled jump in the scattering length leading to a much violent collapse.…”

“…Now we consider the collapse of fermions initiated by a sudden jump in the boson-fermion scattering length from a BF = −12.5 nm to −37.5 nm which can be implemented near a boson-fermion Feshbach resonance. Such boson-fermion Feshbach resonances between 23 Na (boson) and 6 Li (fermion) atoms [23] and between 87 Rb (boson) and 40 K (fermion) atoms [24] have been experimentally observed. These resonances should enable experimental control of the interspecies interactions [24] and hence can be used to increase the attractive force between bosons and fermions which in turn increases the attractive nonlinearities 4 ͱ 2N BF and 4 ͱ 2N FB in Eqs.…”

Formation of fermionic molecules via interisotope Feshbach resonances

“…The underlying molecular state is of a composite fermionic nature, which allows for a new type of crossover physics-the transition of an atomic BEC to a molecular Fermi-type of superfluidity. Recently, Feshbach resonances in a heteronuclear BoseFermi mixture have been observed [8,9], where polar fermionic molecules underly the resonance state.…”

Anderson lattice description of photoassociation in an optical lattice

“…While much work along these lines has concentrated so far on ultracold atoms [2,3], the coherent formation of bosonic or fermionic molecules [4,5,6,7] via either Feshbach resonances [8] or two-photon Raman photoassociation [9] offers an additional path to the study of strongly correlated atoms and molecules [10,11]. Very recently, collective coherent phenomena between an atomic and a molecular gas in an optical lattice have been observed experimentally [12].In this letter we analyze the ground state of a mixture of atomic bosons and two-component fermions coupled to heteronuclear fermionic molecules [13,14] by photoassociation or Feshbach resonance in an optical lattice. We show that this system can be mapped onto the Anderson Lattice Model (ALM), a model that has previously found important applications in the description of heavy electrons and intermediate valence systems in condensed matter physics.…”

“…In this letter we analyze the ground state of a mixture of atomic bosons and two-component fermions coupled to heteronuclear fermionic molecules [13,14] by photoassociation or Feshbach resonance in an optical lattice. We show that this system can be mapped onto the Anderson Lattice Model (ALM), a model that has previously found important applications in the description of heavy electrons and intermediate valence systems in condensed matter physics.…”