Anisotropic thermodynamics of d-wave superconductors in the vortex state

TL;DR

This paper investigates how the thermodynamic properties of 2D d-wave superconductors in a vortex state vary with magnetic field orientation, revealing angular-dependent oscillations that serve as probes of gap symmetry.

Contribution

It introduces a semiclassical approach to analyze anisotropic thermodynamics and predicts angular-dependent oscillations in specific heat related to gap symmetry.

Findings

Fourfold oscillations of specific heat with magnetic field orientation.

Different power laws for density of states depending on field direction.

Orthorhombicity alters the fourfold pattern to twofold.

Abstract

We show that the density of states and the thermodynamic properties of a 2D d-wave superconductor in the vortex state with applied magnetic field $\bf H$ in the plane depend on the angle between $\bf H$ and the order parameter nodes. Within a semiclassical treatment of the extended quasiparticle states, we obtain fourfold oscillations of the specific heat, measurement of which provides a simple probe of gap symmetry. The frequency dependence of the density of states and the temperature dependence of thermodynamic properties obey different power laws for field in the nodal and anti-nodal direction. The fourfold pattern is changed to twofold when orthorhombicity is considered.