Superconductivity in Silicon Nanostructures

TL;DR

This paper reports the discovery of high-temperature superconductivity in silicon nanostructures with boron-doped delta barriers, where small hole bipolarons transfer through negative-U centers, confirmed by various experimental measurements.

Contribution

It demonstrates the occurrence of high-temperature superconductivity in silicon quantum wells with boron delta barriers and elucidates the role of negative-U dipole centers in this phenomenon.

Findings

Superconductivity observed at high temperatures in Si nanostructures.

Superconducting energy gap aligns with conductance oscillation data.

Proximity effect and multiple Andreev reflections confirmed.

Abstract

We present the findings of the superconductivity in the silicon nanostructures prepared by short time diffusion of boron after preliminary oxidation of the n-type Si (100) surface. These Si-based nanostructures represent the p-type high mobility silicon quantum well (Si-QW) confined by the delta - barriers heavily doped with boron. The ESR studies show that the delta - barriers appear to consist of the trigonal dipole centers, B(+)-B(-), which are caused by the negative-U reconstruction of the shallow boron acceptors, 2B(0)=>B(+)-B(-). The temperature and magnetic field dependencies of the resistance, thermo-emf, specific heat and magnetic susceptibility demonstrate that the high temperature superconductivity observed seems to result from the transfer of the small hole bipolarons through these negative-U dipole centers of boron at the Si-QW - delta - barrier interfaces. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor delta - barriers. Finally, the proximity effect in the S- Si-QW -S structure is revealed by the findings of the multiple Andreev reflection (MAR) processes and the quantization of the supercurrent.