Orientational field-dependence of low-lying excitations in mixed state of unconventional superconductors

TL;DR

This paper investigates how the zero energy density of states in unconventional superconductors varies with magnetic field orientation, revealing distinctive patterns that can identify the superconducting gap topology through measurable specific heat oscillations.

Contribution

It provides a theoretical analysis of the orientational dependence of ZEDOS in various unconventional superconductor states, proposing a practical method for gap topology identification.

Findings

ZEDOS varies with field orientation depending on gap topology.

Field rotation in the basal plane causes a ~3% oscillation in ZEDOS for d-wave states.

The results suggest measurable specific heat oscillations in experiments.

Abstract

Orientational field-dependence of the zero energy density of states (ZEDOS) is calculated for superconductors with the polar state (line node), axial state (point node) and 3D d-wave state. Depending on the gap topology and relative field direction the field dependencies of ZEDOS sensitively differ, providing us a useful and practical method to identify the gap topology. It is also demonstrated that for d-wave state the field rotation in the basal plane shows a sizable oscillation ~3% of ZEDOS. This is directly measurable in low-T specific heat experiment in the mixed state.