Mystery of Excess Low Energy States in a Disordered Superconductor in a   Zeeman Field
  Tunneling density of states measurements of disordered superconducting (SC) Al films in high Zeeman fields reveal a significant population of subgap states which cannot be explained by standard BCS theory. We provide a natural explanation of these excess states in terms of a novel disordered Larkin-Ovchinnikov (dLO) phase that occurs near the spin-paramagnetic transition at the Chandrasekhar-Clogston critical field. The dLO superconductor is characterized by a pairing amplitude that changes sign at domain walls. These domain walls carry magnetization and support Andreev bound states, which lead to distinct spectral signatures at low energy. 
Y. L. Loh, N. Trivedi, Y. M. Xiong, P. W. Adams, and G. Catelani
cond-mat.supr-con