Quantum Oscillations and Overcritical Torque Interaction in Sr2RuO4

TL;DR

This study demonstrates the successful detection of quantum oscillations in Sr2RuO4 using piezoresistive microcantilevers and explores the complex torque interactions causing magnetization anomalies, including jumps and damping effects.

Contribution

It introduces a novel application of piezoresistive microcantilever torque magnetometry to Sr2RuO4 and analyzes the overcritical torque interaction effects on magnetization signals.

Findings

Quantum oscillations were observed on all Fermi surface sheets.

Torque interaction causes signal distortions including harmonics and sidebands.

Overcriticality leads to discrete magnetization jumps and damping phenomena.

Abstract

Sr2RuO4 is the only known layered perovskite oxide superconductor without copper; there is strong evidence for an unconventional ("p-wave") pairing mechanism, and it has recently been shown to possess a cylindrical, "quasi-two-dimensional" Fermi surface. Using Sr2RuO4 as a test case for the detection of quantum oscillations with piezoresistive microcantilevers, the piezolever torque magnetometry technique was successfully implemented on a dilution refrigerator. It was possible to reproduce the quantum-oscillatory magnetization data on all three Fermi surface sheets, in a crystal of microgram mass. Moreover, an absolute estimate of the amplitude of the oscillation is provided. We also investigated the phenomenon of torque interaction which distorts the magnetization signal and introduces harmonics and sidebands to the dHvA spectrum. As the torque interaction effect grows in strength, overcriticality is shown to lead to discrete magnetization jumps and to a near-asymptotically damped "sproing" effect.