Conductance asymmetry in point-contacts on epitaxial thin films of Ba(Fe$_{0.92}$Co$_{0.08}$)$_2$As$_2$

TL;DR

This study investigates conductance asymmetry in point-contact spectra of epitaxial Ba(Fe$_{0.92}$Co$_{0.08}$)$_2$As$_2$ thin films, revealing temperature-dependent features linked to the material's normal state properties.

Contribution

It uncovers unique features of the antisymmetric spectrum in ferropnictide superconductors and their evolution with temperature, extending beyond the critical temperature.

Findings

Asymmetric conductance features evolve with temperature.

Features persist up to 30% above $T_c$.

Linked to normal state properties of the material.

Abstract

Point-contact spectroscopy is a powerful tool for probing superconductors. One of the most common observations in the point-contact spectra on the recently discovered ferropnictide superconductors is a large conductance asymmetry with respect to voltage across the point-contact. In this paper we show that the antisymmetric part of the point-contact spectrum between a silver tip and an epitaxial thin film of Ba(Fe$_{0.92}$Co$_{0.08}$)$_2$As$_2$ shows certain unique features. These features have an interesting evolution with increasing temperature up to a temperature that is 30% larger than the critical temperature $T_c$ of the superconductor. We argue that this evolution can be associated with the rich normal state properties of these materials.