Spin fluctuations in Sr2RuO4 from polarized neutron scattering: implications for superconductivity

TL;DR

This study uses polarized neutron scattering to measure spin fluctuations in Sr2RuO4, revealing a significant quasiferromagnetic component but concluding that spin fluctuations alone cannot explain its triplet superconductivity.

Contribution

The paper provides the first comprehensive measurement of the full spin fluctuation spectrum in Sr2RuO4, including quasiferromagnetic signals, and assesses their role in superconductivity.

Findings

Quasiferromagnetic spin fluctuations are stronger than previously thought.

Spin fluctuations alone are insufficient to explain triplet pairing in Sr2RuO4.

The results suggest the need for additional interactions or alternative pairing mechanisms.

Abstract

Triplet pairing in Sr2RuO4 was initially suggested based on the hypothesis of strong ferromagnetic spin fluctuations. Using polarized inelastic neutron scattering, we accurately determine the full spectrum of spin fluctuations in Sr2RuO4. Besides the well-studied incommensurate magnetic fluctuations we do find a sizeable quasiferromagnetic signal, quantitatively consistent with all macroscopic and microscopic probes. We use this result to address the possibility of magnetically-driven triplet superconductivity in Sr2RuO4. We conclude that, even though the quasiferromagnetic signal is stronger and sharper than previously anticipated, spin fluctuations alone are not enough to generate a triplet state strengthening the need for additional interactions or an alternative pairing scenario.