Definitive experimental evidence for two-band superconductivity in MgB2

TL;DR

This study provides definitive experimental evidence for two-band superconductivity in MgB2 by measuring distinct superconducting gaps on different bands using ARPES, confirming the role of k-dependent electron-phonon coupling.

Contribution

It is the first to directly measure and confirm the two-band superconductivity in MgB2 through high-resolution ARPES experiments.

Findings

Superconducting gaps of 5.5 meV and 2.2 meV on s- and p-bands

Both gaps close at the bulk transition temperature

Validation of k-dependent electron-phonon coupling as the origin

Abstract

The superconducting gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy (ARPES). The momentum(k)-resolving capability of ARPES enables us to identify the s- and p-orbital derived bands predicted from band structure calculations and to successfully measure the superconducting gap on each band. The results show that superconducting gaps with values of 5.5 meV and 2.2 meV open on the s-band and the p-band, respectively, but both the gaps close at the bulk transition temperature, providing a definitive experimental evidence for the two-band superconductivity in MgB2. The experiments validate the role of k-dependent electron-phonon coupling as the origin of multiple-gap superconductivity in MgB2.