$^{6}$Atominstitut, TU-Wien, Stadionallee 2, 1020 Vienna, Austria 

# rf-field-induced Feshbach resonances 

T. V. Tscherbul, 1, 2 T. Calarco, 3 I. Lesanovsky, 4 

R. V. Krems, 5 A. Dalgarno, 1, 2 and J. Schmiedmayer 6 

$^{1}$Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138, USA 

$^{2}$ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA ∗ 

$^{3}$Institute of Quantum Information Processing, Ulm University, D-89081 Ulm, Germany 

$^{4}$School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, UK 

$^{5}$Department of Chemistry, University of British Columbia, Vancouver BC, V6T 1Z1, Canada 

(Dated: November 1, 2018) 

## Abstract 

A rigorous quantum theory of atomic collisions in the presence of radio frequency (rf) magnetic fields is developed and applied to elucidate the effects of combined dc and rf magnetic fields on ultracold collisions of Rb atoms. We show that rf fields can be used to induce Feshbach resonances, which can be tuned by varying the amplitude and frequency of the rf field. The rf-induced Feshbach resonances occur also in collisions of atoms in low-field-seeking states at moderate rf field strengths easily available in atom chip experiments, which opens up the world of tunable interactions to magnetically trappable atomic quantum gases. 

PACS numbers: 

