Parity of the Pairing Bosons in a High-Temperature Superconductor

TL;DR

This study reveals that in a high-temperature superconductor, the dominant scattering mechanism involves odd collective spin excitations rather than phonons, indicating a magnetic pairing mechanism.

Contribution

It provides experimental evidence for the magnetic nature of the pairing mediator in a bilayer high-TC superconductor using angle-resolved photoemission spectroscopy.

Findings

Scattering rates differ between bonding and antibonding bands.

The dominant scattering channel is odd with respect to layer exchange.

Results support a magnetic, spin-excitation pairing mechanism.

Abstract

We report the observation of a novel effect in the bilayer Pb-Bi2212 high-TC superconductor by means of angle-resolved photoemission with circularly polarized excitation. Different scattering rates, determined as a function of energy separately for the bonding and antibonding copper-oxygen bands, strongly imply that the dominating scattering channel is odd with respect to layer exchange within a bilayer. This is inconsistent with a phonon-mediated scattering and favours the participation of the odd collective spin excitations in the scattering mechanism in near-nodal regions of the k-space, suggesting a magnetic nature of the pairing mediator.