Local Nodal Cooper Pairs in Multiorbital Systems

We show the occurrence of a new class of superconductivity in multiorbital systems, focusing on non-Kramers f2 states. The Cooper pairs in this class of superconductivity are mainly local pairs with the same symmetry as the local f2 ground states. When the local ground state is an anisotropic representation, the superconducting gap has nodes on the Fermi surface. This nodal superconductivity is mediated by the strong on-site interorbital attractions arising from the negative-U physics, generalized in multiorbital systems. We show that this is realized in a simple two-orbital model with antiferro Hund's coupling and enhanced inter-orbital interactions derived via a systematic local down folding. Finally, we briefly discuss superconductivity in Pr-1-2-20 compounds, UBe13, and PrOs4Sb12, in view of the present mechanism.