Doping the multiorbital Hund's coupled impurity: an exploration of non-Fermi liquid ground states*

Motivated by the relevance of Hund’s coupling in Iron-based superconductors, we revisit the problem of a multiorbital Anderson impurity with Hund’s interaction. Using large-N and Schwinger boson techniques, we study the ground state and thermodynamic properties of this system in the mixed valence regime. The physics is characterized by the interplay of Hund’s coupling, which tends to form large moments by aligning the spins of the impurity, and the Kondo effect, which leads to the low-temperature screening of the moments. In the mixed-valence regime, previous NRG studies have found evidence that the system is in proximity to a non-Fermi liquid fixed point. We investigate whether such features survive in the large-N limit. We also explore the possibility that the interplay of the non-integer occupation of orbital sites with a significant Hund’s coupling can generate retarded on-site pairing correlations for the conduction electrons.