Synthetic dimensions and spin-orbit coupling with an optical clock   transition
  We demonstrate a novel way of synthesizing spin-orbit interactions in ultracold quantum gases, based on a single-photon optical clock transition coupling two long-lived electronic states of two-electron $^{173}$Yb atoms. By mapping the electronic states onto effective sites along a synthetic "electronic" dimension, we have engineered synthetic fermionic ladders with tunable magnetic fluxes. We have detected the spin-orbit coupling with fiber-link-enhanced clock spectroscopy and directly measured the emergence of chiral edge currents, probing them as a function of the magnetic field flux. These results open new directions for the investigation of topological states of matter with ultracold atomic gases. 
L. F. Livi, G. Cappellini, M. Diem, L. Franchi, C. Clivati, M.   Frittelli, F. Levi, D. Calonico, J. Catani, M. Inguscio, L....
cond-mat.quant-gas physics.atom-ph quant-ph