Basal-Plane Magnetic Anisotropies of High-kappa d-Wave Superconductors in a Mixed State: A Quasiclassical Approach

TL;DR

This paper investigates the in-plane magnetic anisotropies of layered d-wave superconductors in a mixed state using a quasiclassical approach, revealing how magnetization and torque oscillations relate to node positions and anisotropies.

Contribution

It provides a detailed analysis of magnetization and torque anisotropies in d-wave superconductors, linking oscillation patterns to node positions and proposing torque measurements to detect in-plane anisotropies.

Findings

Both magnetization and torque show fourfold oscillations with field angle.

The sign of torque oscillation remains constant between Hc1 and Hc2.

Magnetization oscillation sign changes between Hc1 and Hc2.

Abstract

We study the basal-plane anisotropies of reversible magnetization and torque in a mixed state of layered d-wave superconductors based on the quasiclassical version of the BCS-Gor'kov theory. Both the longitudinal magnetization ($M_L$) and torque ($\tau$) show fourfold oscillations as a function of the field angle $\chi$. The relationship between the node position and the oscillatory patterns shown by $M_L$ and $\tau$ is clarified. It is also shown that the sign of the $\tau (\chi)$-oscillation does not change between $H_{c1}$ and $H_{c2}$, while the sign of the $M_L (\chi)$-oscillation changes. The newly obtained result for $\tau$ indicates that the torque experiment can allow us to detect the in-plane anisotropies of $H_{c2}$ even in a material with strong fluctuations such as cuprate or organic superconductors, where the $H_{c2}$ itself cannot be determined experimentally.