Observation of superconducting gap in boron-doped diamond by laser-excited photoemission spectroscopy

TL;DR

This study used laser-excited photoemission spectroscopy to observe a superconducting gap in boron-doped diamond, revealing disorder effects that broaden the gap feature and affect quasiparticle coherence.

Contribution

First direct observation of a superconducting gap in boron-doped diamond using ultrahigh resolution laser photoemission spectroscopy.

Findings

Superconducting gap of approximately 0.78 meV observed below 11 K.

The gap feature is broad, and quasiparticle peaks are not well-defined.

Disorder effects likely influence the superconducting properties in this system.

Abstract

We have investigated the low energy electronic state of a boron-doped diamond thin film by the ultrahigh resolution laser-excited photoemission spectroscopy. We observed a clear shift of the leading edge below 11 K indicative of a superconducting gap opening ($\Delta \sim 0.78$ meV at 4.5 K). The gap feature is significantly broad and the well-defined quasiparticle peak is not recognizable even at the lowest temperature of measurement 4.5 K. We discuss our result in terms of possible disorder effect on superconductivity in this system.