Comment on "Anisotropic s-wave superconductivity in MgB_2"

TL;DR

This paper analytically examines how anisotropy in the superconducting order parameter affects the heat capacity jump in MgB_2, providing a method to determine gap anisotropy from specific heat data.

Contribution

It derives an analytical expression for the heat capacity jump considering anisotropic superconductivity within a specific model, enabling direct gap anisotropy measurement.

Findings

Analytical formula for heat capacity jump with anisotropy

Graphical relation between jump and gap ratio

Method to determine gap anisotropy from experiments

Abstract

An analytical result for renormalization of the jump of the heat capacity Delta C/C_N by the anisotropy of the order parameter is derived in the framework of the model proposed by Haas and Maki [Phys. Rev. B 65, 020502(R) (2001)], for both prolate and oblate anisotropy. The graph of Delta C/C_N versus the ratio of the gaps on the equator and the pole, Delta_e/Delta_p, of the Fermi surface allows a direct determination of the gap anisotropy parameter Delta_e/Delta_p using data from specific heat measurements.