Superconductivity in doped spin multimer systems

TL;DR

This paper demonstrates that doped spin multimer systems, modeled as hardcore bosons, show signs of superconductivity through analytical and numerical methods, highlighting the role of binding energy in pair formation.

Contribution

It introduces a universal framework for understanding superconductivity in complex spin systems using the hardcore boson model and validates it with the double Kondo lattice model.

Findings

Pairing states persist across a range of parameters.

Binding energies lead to similar pair correlations regardless of local spin details.

Superconductivity signatures are promising in hole-doped multimer systems.

Abstract

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, which can be mapped onto the universal hardcore boson model in the strong-binding-energy limit, exhibit promising signatures of superconductivity. We analytically and numerically demonstrate this concept 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 suggest useful guidelines for research on superconductivity.