Strength of the Spin-Fluctuation-Mediated Pairing Interaction in a High-Temperature Superconductor

TL;DR

This study quantitatively links spin fluctuations to high-temperature superconductivity in cuprates, showing that a single coupling parameter can explain spectral features and predict transition temperatures above 150 K.

Contribution

It provides a self-consistent analysis of charge and spin spectra in YBa2Cu3O6.6, establishing the strength of spin-fluctuation-mediated pairing as sufficient for high Tc.

Findings

Quantitative link between high-energy spin excitations and fermionic band kinks.

Superconducting Tc estimated to exceed 150 K using the spin-fermion coupling.

A unified description of charge and spin spectra with a single parameter.

Abstract

Theories based on the coupling between spin fluctuations and fermionic quasiparticles are among the leading contenders to explain the origin of high-temperature superconductivity, but estimates of the strength of this interaction differ widely. Here we analyze the charge- and spin-excitation spectra determined by angle-resolved photoemission and inelastic neutron scattering, respectively, on the same crystals of the high-temperature superconductor YBa2Cu3O6.6. We show that a self-consistent description of both spectra can be obtained by adjusting a single parameter, the spin-fermion coupling constant. In particular, we find a quantitative link between two spectral features that have been established as universal for the cuprates, namely high-energy spin excitations and "kinks" in the fermionic band dispersions along the nodal direction. The superconducting transition temperature computed with this coupling constant exceeds 150 K, demonstrating that spin fluctuations have sufficient strength to mediate high-temperature superconductivity.