How to measure a spinon Fermi surface
  We propose an experiment to identify the potential existence of a spinon Fermi surface by looking for oscillatory coupling between two ferromagnets via a spin liquid spacer. Three candidate spin liquids are investigated, and it is found that in all cases, long period oscillations should be present, the period of which would identify the Fermi wavevector of the spinon surface. 
M. R. Norman, T. Micklitz