The superconducting states, corresponding to d(k) =  (kx + iky) (left) and d(k) = kx ky (right), have different spin orientations and total angular momentum.  The  (kx + iky) state has an angular momentum along the z-axis (thick arrow) and spin perpendicular in the plane (thin arrows).  Its total angular momentum therefore has a value of 1 and points along the z-axis. The kx ky state has vanishing total angular momentum because the orbital angular momentum is compensated by the spins of the Cooper pair.  Both states represent equal-spin-pairing states, but have very different physical properties. Experiments identify the superconducting phase in Sr2RuO4 as being of the type in the left panel--that is, a state with finite angular momentum. 

                                 © 2001 American Institute of Physics

          Strontium ruthenate