Two-Band Superconductivity in MgB2

TL;DR

This paper provides experimental evidence for two-band superconductivity in MgB2, revealing two distinct energy gaps and their temperature evolution, supporting the multigap model of superconductivity in this material.

Contribution

The study experimentally confirms the existence of two superconducting gaps in MgB2 and their behavior, supporting the multiband superconductivity model.

Findings

Two distinct energy gaps at 2.3 meV and 7.1 meV were observed.

Both gaps vanish at the bulk critical temperature, following BCS behavior.

Fermi-surface sheet dependence is crucial for understanding MgB2 superconductivity.

Abstract

The study of the anisotropic superconductor MgB2 using a combination of scanning tunneling microscopy and spectroscopy reveals two distinct energy gaps at Delta1=2.3 meV and Delta2=7.1 meV. Different spectral weights of the partial superconducting density of states (PDOS) are a reflection of different tunneling directions in this multi-band system. Our experimental observations are consistent with the existence of two-band superconductivity in the presence of interband superconducting pair interaction and quasiparticle scattering. Temperature evolution of the tunneling spectra follows the BCS scenario with both gaps vanishing at the bulk Tc. Indeed, the study of tunneling junctions exhibiting only the small gap (c-axis tunneling) clearly and reproducibly show that this gap persists up to the bulk Tc. The data confirm the importance of Fermi-surface sheet dependent superconductivity in MgB2 proposed in the multigap model by Liu et al.