Orbital Resonant Valence Bond States: Emergence of Superconductivity in Doped Multiorbital Chains

We introduce an "Orbital Resonant Valence Bond" (ORVB) state for two-orbital Hubbard models in one dimension that explains the recent computational discovery of pairing in these systems when hole doped. Our Ansatz is based on a mathematical expression where the undoped (one electron per orbital) quantum state of two nearest-neighbor (NN) sites coupled into a global spin singlet is rewritten exactly employing only spin-1/2 singlets linking NN orbitals. Generalizing to longer chains provides an ORVB variational state that can be visualized geometrically expressing our chain as a two-leg ladder, with one orbital per leg. As in Anderson's resonating valence-bond state, ORVB describes the undoped ground state as a "liquid" of preformed NN singlet pairs that via doping become mobile. Real materials with one-dimensional susbstructures, two near-degenerate orbitals, and intermediate Hubbard $U/W$ strengths -- $W$ the carrier's bandwidth -- could realize the ORVB state if on-site anisotropies are small. If these anisotropies are robust, spin-triplet pairing is possible.