Vortex State and Field-Angle Resolved Specific Heat Oscillation for H // ab in d-Wave Superconductors

TL;DR

This paper investigates vortex lattice structures, local density of states, and specific heat oscillations in d-wave superconductors under magnetic fields, using selfconsistent Eilenberger theory, to identify gap node positions and effects of paramagnetism.

Contribution

It provides a detailed theoretical analysis of vortex states and specific heat oscillations considering paramagnetic effects, aiding experimental identification of gap node directions.

Findings

Vortex lattice structure depends on the angle between magnetic field and gap nodes.

Sign change in specific heat oscillation explained by including paramagnetic effects.

Field-angle resolved specific heat can identify the superconducting gap node positions.

Abstract

When magnetic field is applied parallel to the ab plane in d_{x^2-y^2}-wave superconductors, the transition of stable vortex lattice structure, spatial structure of local density of states, and specific heat oscillation by rotation of magnetic field orientation are investigated by quantitative calculations based on the selfconsistent Eilenberger theory. We estimate how the vortex state changes depending on the relative angle between the node-direction of the superconducting gap and magnetic field orientation. To reproduce the sign-change of specific heat oscillation observed in CeCoIn_5, our study is done by including strong paramagnetic effect. The quantitative theoretical calculations give decisive information to analyze the experimental data on the field-angle dependence, and establish the angle-resolved specific heat experiment as a spectroscopic means to identify the node-position of the superconducting gap.