MgB2 Energy Gap Determination by Scanning Tunneling Spectroscopy

TL;DR

This paper uses scanning tunneling spectroscopy to measure the energy gaps in MgB2, revealing evidence for two distinct superconducting gaps and their temperature dependence, supporting a two-band superconductivity model.

Contribution

It provides detailed tunneling spectroscopy measurements of MgB2, demonstrating the existence of two superconducting gaps and their characteristics, which advances understanding of its superconducting properties.

Findings

Identification of a smaller gap delta=2.3-2.8 meV

Evidence for a larger gap delta=7.2 meV

Confirmation of two-band superconductivity in MgB2

Abstract

We report scanning tunneling spectroscopy (STS) measurements of the gap properties of both ceramic MgB2 and c-axis oriented epitaxial MgB2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunneling spectroscopy of superconductor-insulator-superconductor (S-I-S) junctions formed in two ways in addition to normal metal-insulator-superconductor (N-I-S) junctions. We find a gap delta=2.3-2.8 meV, with spectral features and temperature dependence that are consistent between S-I-S junction types. In addition, we observe evidence of a second, larger gap, delta=7.2 meV, consistent with a proposed two-band model.