Orbital Feshbach Resonance in Alkali-Earth Atoms

For a mixture of alkali-earth atomic gas in the long-lived excited state ³P₀ and the ground state ¹S₀, in addition to nuclear spin, another "orbital" index is introduced to distinguish these two internal states. In this Letter we propose a mechanism to induce Feshbach resonance between two atoms with different orbital and nuclear spin quantum numbers. Two essential ingredients are the interorbital spin-exchange process and orbital dependence of the Landé g factors. Here the orbital degrees of freedom plays a similar role as the electron spin degree of freedom in magnetic Feshbach resonance in alkali-metal atoms. This resonance is particularly accessible for the ¹⁷³Yb system. The BCS-BEC crossover in this system requires two fermion pairing order parameters, and displays a significant difference compared to that in an alkali-metal system.