The Triplet Resonating Valence Bond State and Superconductivity in Hund's Metals: I Concept and Symmetries

A central idea in strongly correlated systems is that doping a Mott insulator leads to a superconductor by transforming the resonating valence bonds (RVBs) into spin-singlet Cooper pairs. Here, we argue that a spin-triplet RVB (tRVB) state, driven by spatially, or orbitally anisotropic ferromagnetic interactions can provide the parent state for triplet superconductivity. One of the new features of the concept, is that triplet RVB bonds can resonate into the interior of an atom, where they are supported as Hund's coupled triplet states between orbitals at the same site. Remarkably though, simple symmetry arguments due to P. W. Anderson, mean that such a process can only develop coherence with triplet pairs on the Fermi surfacce, if the there are two symmetry related atoms per unit cell, leading to a state that has staggered structure of onsite pair correlations that can be detected using Josephson tunneling. A natural candidate for this physics are the iron based superconductors, as will be described in the two following talks [1].

[1]P. Coleman, Y. Komijani, E. Konig, arXiv :1910.03168