Anisotropic Diamagnetic Response in Type-II Superconductors with Gap and Fermi-Surface Anisotropies

TL;DR

This paper demonstrates that field-angle-resolved magnetization measurements can serve as a spectroscopic tool to identify gap structures in anisotropic type-II superconductors, revealing oscillation patterns linked to anisotropies.

Contribution

It introduces a microscopic calculation showing how magnetization oscillations reflect gap and Fermi surface anisotropies in superconductors.

Findings

Four-fold oscillation in magnetization reflects anisotropies.

Sign of oscillation changes between $H_{c1}$ and $H_{c2}$.

Application to borocarbides discussed.

Abstract

Effects of anisotropic gap structures on a diamagnetic response are investigated in order to demonstrate that the field-angle-resolved magnetization ($M_L(\chi)$) measurement can be used as a spectroscopic method to detect gap structures. Our microscopic calculation based on the quasiclassical Eilenberger formalism reveals that $M_L(\chi)$ in a superconductor with four-fold gap displays a four-fold oscillation reflecting the gap and Fermi surface anisotropies, and the sign of this oscillation changes at a field between $H_{c1}$ and $H_{c2}$. As a prototype of unconventional superconductors, magnetization data for borocarbides are also discussed.