A novel class of singlet superconductors
  A new class of singlet superconductors with a gap function $\Delta(\bk, \omega_n)$ which is {\it odd} in both momentum and Matsubara frequency is considered. Some of the physical properties of this superconductivity are discussed and it is argued that: i) the electron-phonon interaction can produce this kind of pairing, ii) in many cases there is no gap in the quasiparticle spectrum, iii) these superconductors will exhibit a Meissner effect. 
Alexander Balatsky and Elihu Abrahams