Magnon-Mediated Superconductivity in the Infinite-$U$ Triangular Lattice

TL;DR

This paper demonstrates that the infinite-U triangular-lattice Hubbard model can host a magnon-mediated superconducting state formed by bound states of two holes and one magnon, stabilized by next-nearest-neighbor hopping.

Contribution

It reveals a novel magnon-mediated superconductivity mechanism in the Hubbard model, supported by large-scale DMRG calculations and stabilized by kinetic frustration.

Findings

Identification of a stable $s$-wave bound state with substantial binding energy

Observation of a magnetization plateau indicating a gas of bound states

Detection of quasi-long-range superconducting order with power-law pair correlations

Abstract

We demonstrate that the infinite-$U$ triangular-lattice Hubbard model supports a superconducting state built from tightly bound Cooper pairs composed of two holes and one magnon ($2h1m$). Building on the seminal prediction of repulsively bound $2h1m$ states, we show that next-nearest-neighbor hopping $t_{2}$ coherently mixes symmetry-related configurations, stabilizing an $s$-wave bound state with substantial binding energy and a light effective mass. Large-scale DMRG calculations at finite doping identify a magnetization plateau corresponding to a gas of such bound states and quasi--long--range superconducting order with power-law $2h1m$ pair correlations. Our results establish a magnon-mediated superconducting mechanism driven by kinetic frustration, with immediate detectable signatures for moir\'e Hubbard materials and ultracold-atom simulators.