Tunneling spectroscopy and vortex imaging in boron-doped diamond

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Boron-doped diamond is a promising material for electronic applications.
• Understanding its superconducting properties is crucial for technological advancement.
• Previous studies have hinted at superconductivity, but detailed spectroscopic evidence was lacking.

Purpose of the Study:

• To investigate the superconducting properties of single-crystalline boron-doped diamond.
• To characterize the superconducting gap and its temperature dependence.
• To explore the behavior of vortices in this material.

Main Methods:

• Low-temperature scanning tunneling spectroscopy (LT-STS) performed below 100 mK.
• Measurement of the tunneling density of states.
• Vortex imaging using LT-STS in a low magnetic field.

Main Results:

• Observation of a distinct superconducting gap in the tunneling density of states.
• The temperature evolution of the superconducting order parameter aligns with weak-coupling Bardeen-Cooper-Schrieffer (BCS) theory, with Delta(0)/kBTc ≈ 1.74.
• Localized states were detected within vortex cores, which is unusual for a superconductor considered 'dirty'.

Conclusions:

• Single-crystalline boron-doped diamond exhibits clear signs of superconductivity.
• The material behaves as a weak-coupling superconductor according to BCS theory.
• The presence of localized states in vortex cores suggests complex physics beyond standard dirty superconductor models.