Prediction of superconductivity in the hole-doped two-orbital Hubbard chain

We investigate pairing tendencies in the two-orbital Hubbard chain at intermediate repulsive interaction U, and for degenerate orbitals. At half-filling, the Hund's coupling, J_H, generates effective spin-1 moments, with antiferromagnetic correlations between sites. Thus the system becomes an electronic generalization of Haldane's spin-1 chain. Using large-scale density matrix renormalization group calculations, we study the system's behavior under light hole doping. For U=1.6 in units of the non-interacting bandwidth and J_H≥0.275 we find that singlet pairing dominates the long-distance physics, establishing this system as a promising platform for repulsively mediated superconductivity. We provide numerical evidence that the system approaches a Luther-Emery liquid state at large system sizes, similarly to the behavior of doped one-orbital two-leg ladders at weak coupling. For large systems, the fitted central charge approaches one, indicating a single gapless mode as is expected for the Luther-Emery state. Exponents characterizing the power-law decays of singlet pair-pair and charge density-density correlations are determined, and found to approximately satisfy the Luther-Emery identity.