Inelastic neutron scattering study of magnetic excitations in Sr$_2$RuO$_4$

TL;DR

This study uses inelastic neutron scattering to analyze magnetic excitations in Sr$_2$RuO$_4$, revealing incommensurate peaks linked to Fermi surface nesting, and indicates proximity to magnetic instability without quantum criticality.

Contribution

It provides detailed experimental data on magnetic fluctuations in Sr$_2$RuO$_4$ and compares findings with RPA calculations, highlighting the material's closeness to magnetic instability.

Findings

Magnetic fluctuations are dominated by incommensurate peaks.

The incommensurate signal matches RPA calculations.

Magnetic response remains unchanged below the superconducting transition.

Abstract

Magnetic excitations in \srruo ~ have been studied by inelastic neutron scattering. The magnetic fluctuations are dominated by incommensurate peaks related to the Fermi surface nesting of the quasi-one-dimensional $d_{xz}$- and $d_{yz}$-bands. The shape of the incommensurate signal agrees well with RPA calculations. At the incommensurate {\bf Q}-positions the energy spectrum considerably softens upon cooling pointing to a close magnetic instability : \srruo ~does not exhibit quantum criticality but is very close to it. $\omega / T$-scaling may be fitted to the data for temperatures above 30 K. Below the superconducting transition, the magnetic response at the nesting signal is not found to change in the energy range down to 0.4meV.