Intertwined Superconductivity and Magnetism from Repulsive Interactions in Kondo Bilayers
arxiv(2024)
Abstract
While superconductors are conventionally established by attractive
interactions, higher-temperature mechanisms for emergent electronic pairing
from strong repulsive electron-electron interactions remain under considerable
scrutiny. Here, we establish a strong-coupling mechanism for intertwined
superconductivity and magnetic order from purely repulsive interactions in a
Kondo-like bilayer system, composed of a two-dimensional Mott insulator coupled
to a layer of weakly-interacting itinerant electrons. Combining large scale
DMRG and Monte Carlo simulations, we find that superconductivity persists and
coexists with magnetism over a wide range of interlayer couplings. We classify
the resulting rich phase diagram and find 2-rung antiferromagnetic and 4-rung
antiferromagnetic order in one-dimensional systems along with a phase
separation regime, while finding that superconductivity coexists with either
antiferromagnetic or ferromagnetic order in two dimensions. Remarkably, the
model permits a rigorous strong-coupling analysis via localized spins coupled
to charge-2e bosons through Kugel-Khomskii interactions, capturing the pairing
mechanism in the presence of magnetism due to emergent attractive interactions.
Our numerical analysis reveals that pairing remains robust well beyond the
strong-coupling regime, establishing a new mechanism for superconductivity in
coupled weakly- and strongly-interacting electron systems, relevant for
infinite-layer nickelates and superconductivity in moire multilayer
heterostructures.
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