Tunneling Spectroscopy and Vortex Imaging in Boron-Doped Diamond

TL;DR

This study uses low-temperature scanning tunneling spectroscopy to investigate superconductivity in boron-doped diamond, revealing a BCS-like gap and unexpected vortex core states in a dirty superconductor.

Contribution

First to perform detailed tunneling spectroscopy and vortex imaging on single-crystalline boron-doped diamond at millikelvin temperatures.

Findings

Superconducting gap follows weak coupling BCS law.

Localized states observed inside vortex cores.

Superconductivity persists in a dirty diamond superconductor.

Abstract

We present the first scanning tunneling spectroscopy study of single-crystalline boron doped diamond. The measurements were performed below 100 mK with a low temperature scanning tunneling microscope. The tunneling density of states displays a clear superconducting gap. The temperature evolution of the order parameter follows the weak coupling BCS law with $\Delta(0)/k_B T_c \simeq 1.74$. Vortex imaging at low magnetic field also reveals localized states inside the vortex core that are unexpected for such a dirty superconductor.