How to detect gap nodes of a superconductor by angle-resolved specific heat experiment?

TL;DR

This paper presents a theoretical method using angle-resolved specific heat measurements in the mixed state of type II superconductors to identify the location of gap nodes and distinguish between nodal and anisotropic gaps.

Contribution

It introduces a microscopic calculation approach solving the Eilenberger equation to interpret specific heat oscillations for gap node detection.

Findings

Oscillation amplitude varies with magnetic field, indicating gap structure.

Oscillation phase reveals the position of gap minima on the Fermi surface.

Method distinguishes between nodal and anisotropic gaps.

Abstract

The specific heat oscillation in the mixed state of type II superconductors is studied theoretically when rotating field within a plane containing gap minimum and maximum. The calculations are performed microscopically by solving quasi-classical Eilenberger equation for vortex lattices. The field dependence of the oscillation amplitude can discriminate between the nodal and anisotropic gap with a finite minimum and the oscillation phase gives the gap minimum position on the Fermi surface. These also provide a way to separate out the anisotropic behavior due to the Fermi velocity.