Symmetry of the order parameter in superconducting ZrZn_2

TL;DR

This paper uses symmetry analysis to predict how the superconducting gap nodes in ferromagnetic ZrZn_2 depend on magnetization direction, proposing ultrasound measurements to determine the gap symmetry.

Contribution

It introduces a symmetry-based framework to analyze the superconducting order parameter in ferromagnetic ZrZn_2, linking magnetization direction to gap node locations.

Findings

Order parameter has zeros when magnetization is along z axis.

Gap node locations depend on magnetization direction.

Ultrasound attenuation can identify gap symmetry.

Abstract

We apply symmetry considerations to study the possible superconducting order parameters in ferromagnetic ZrZn_2. We predict that the presence and the location of the superconducting gap nodes depend on the direction of magnetization M. In particular, if M is directed along the z axis, then the order parameter should always have zeros. We also discuss how to determine the gap symmetry in ZrZn_2 using ultrasound attenuation measurements.