Microscopic Evidence for Evolution of Superconductivity by Effective Carrier Doping in Boron-doped Diamond:11B-NMR study

TL;DR

This study uses 11B-NMR to provide microscopic evidence that effective carrier doping at specific boron sites in boron-doped diamond induces superconductivity, highlighting the role of substitutional B(1) sites.

Contribution

It reveals that superconductivity in boron-doped diamond is driven by carriers from B(1) substitutional sites, distinguishing their role from B(2) sites through NMR analysis.

Findings

Effective carriers originate from B(1) substitutional sites.

B(2) sites do not contribute to superconductivity.

Superconductivity evolution correlates with carrier density from B(1) sites.

Abstract

We have investigated the superconductivity discovered in boron (B)-doped diamonds by means of 11B-NMR on heteroepitaxially grown (111) and (100) films. 11B-NMR spectra for all of the films are identified to arise from the substitutional B(1) site as single occupation and lower symmetric B(2) site substituted as boron+hydrogen(B+H) complex, respectively. A clear evidence is presented that the effective carriers introduced by B(1) substitution are responsible for the superconductivity, whereas the charge neutral B(2) sites does not offer the carriers effectively. The result is also corroborated by the density of states deduced by 1/T1T measurement, indicating that the evolution of superconductivity is driven by the effective carrier introduced by substitution at B(1) site.