Superconductivity in silicon nanostructures

TL;DR

This paper reports the discovery of superconductivity in silicon nanostructures created by boron diffusion, highlighting the role of negative-U centers and two-dimensional hole transport in enabling superconductivity.

Contribution

It demonstrates superconductivity in silicon quantum wells with delta-doped boron barriers and elucidates the underlying mechanisms involving negative-U centers and hole tunneling.

Findings

Superconductivity observed in boron-doped silicon nanostructures.

Correlation gaps consistent with magnetic susceptibility data.

Strong diamagnetism indicating superconducting state.

Abstract

We present the findings of the superconductivity observed in the silicon nanostructures prepared by short time diffusion of boron on the n-type Si(100) surface. These Si-based nanostructures represent the p-type ultra-narrow self-assembled silicon quantum wells, 2nm, confined by the delta - barriers heavily doped with boron, 3nm. The EPR and the thermo-emf studies show that the delta - barriers appear to consist of the trigonal dipole centres, which are caused by the negative-U reconstruction of the shallow boron acceptors. Using the CV and thermo-emf techniques, the transport of two-dimensional holes inside SQW is demonstrated to be accompanied by single-hole tunneling through these negative-U centres that results in the superconductivity of the delta - barriers. The values of the correlation gaps obtained from these measurements are in a good agreement with the data derived from the temperature and magnetic field dependencies of the magnetic susceptibility, which reveal a strong diamagnetism and additionally identify the superconductor gap value.