Spin-orbit-coupled two-electron Fermi gases of ytterbium atoms

We demonstrate all-optical implementation of spin-orbit coupling (SOC) in a two-electron Fermi gas of Yb-173 atoms by coupling two hyperfine ground states with a narrow optical transition. Due to the SU(N) symmetry of the (1) S-0 ground-state manifold which is insensitive to external magnetic fields, an optical ac Stark effect is applied to split the ground spin states, which exhibits a high stability compared with experiments on alkali-metal and lanthanide atoms, and separate out an effective spin-1/2 subspace from other hyperfine levels for the realization of SOC. The dephasing spin dynamics when a momentum-dependent spin-orbit gap is suddenly opened and the asymmetric momentum distribution of the spin-orbit-coupled Fermi gas are observed as a hallmark of SOC. The realization of all-optical SOC for ytterbium fermions should offer a route to a long-lived spin-orbit-coupled Fermi gas and greatly expand our capability of studying spin-orbit physics with alkaline-earth-metal-like atoms.