Electronic density of states at the surface of a superconductor in contact with a magnetic insulator

A threefold splitting of the main conductance peak has been observed in symmetric tunneling junctions with Pb electrodes and barriers of Ho(OH${)}_3$, a material which is a ferromagnet in bulk. The results are consistent with the existence of an electronic bound state in each of the electrodes near the barrier at an energy below that of the gap.