Binding energy, which quantifies pair formation, is a key factor in the emergence of superconductivity. Here, we show that even when multiple spins are complexly coupled, hole-doped systems can be mapped, in the strong-binding-energy limit, onto an effective hardcore boson model equivalent to the XXZ model, and exhibit promising signatures of superconductivity. We demonstrate this theory analytically and numerically in the double Kondo lattice model. Using the density-matrix renormalization group method, we show that a pairing state is maintained via a crossover even for parameters away from the strong-coupling regime. Additionally, we find that once binding energies are sufficiently generated, pair correlations develop similarly regardless of the details of local spin correlations. Our findings provide useful insights into the mechanism of superconductivity.

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• Hard-core bosons
• Pairing mechanisms
• Spin-singlet pairing
• Superconductivity
• Bose-Einstein condensates
• Strongly correlated systems
• Density matrix renormalization group
• Hubbard model
• Kondo lattice model