Production of Feshbach molecules induced by spin–orbit coupling in Fermi gases

Abstract

The creation of Feshbach molecules by exploiting engineered spin–orbit coupling in a spin-polarized Fermi gas advances the experimental study of topological superfluidity in ultracold gases. The search for topological superconductors is a challenging task1,2. One of the most promising directions is to use spin–orbit coupling through which an s-wave superconductor can induce unconventional p-wave pairing in a spin-polarized metal3,4. Recently, synthetic spin–orbit couplings have been realized in cold-atom systems5,6,7,8,9,10,11,12,13,14,15,16 where instead of a proximity effect, s-wave pairing originates from a resonant coupling between s-wave molecules and itinerant atoms17. Here we demonstrate a dynamic process in which spin–orbit coupling coherently produces s-wave Feshbach molecules from a fully polarized Fermi gas, and induces a coherent oscillation between these two. This demonstrates experimentally that spin–orbit coupling does coherently couple singlet and triplet states, and implies that the bound pairs of this system have a triplet p-wave component, which can become a topological superfluid by further cooling to condensation and confinement to one dimension.