Mesoscopic superconductivity above 10 K in silicon point contacts

Abstract

Silicon, perhaps the most ubiquitously used material in the digital age of today, has also been a material of choice for testing the fundamental differences between various electronic ground states, e.g., metals and insulators. This is mainly because ultimate control has been achieved in growing extremely pure silicon crystals and doping them with varying concentrations of charge carriers and their mobility. Here, we show that by forming mesoscopic point contacts with non-superconducting metals on insulating (doped) silicon, it is possible to obtain a superconducting phase with a remarkably high critical temperature above 10 K and an average superconducting energy gap of 2 meV. Apart from its importance in advancing the understanding of nanoscale superconductivity, this discovery is also expected to boost the efforts to realize silicon based superconducting devices with far reaching application potential.

Transport across meso-junctions of highly doped Si with different superconductors

“…To understand these anomalous features in the PCAR spectra, it becomes pertinent to ask, what is the origin of the large gap of In observed for all contacts with highly doped Si. Can these observations be explained i) simply as experimental artefacts in soft PC spectroscopy or ii) by the fact that highly doped Si might show tip induced superconductivity (TIS) consistent with the recent report by Sirohi et al 33 or iii) on the basis of the Schottky barrier present at the Sm-Sc interface 30 or iv) by the presence of a second superconducting phase appearing at the Sm-Sc interface induced by the proximity effect 9 .…”

“…This indicated that the observations for the n++Si-In junction were reflective of a Sm-Sc interface. Furthermore, tip induced superconductivity reported from point contact measurements in highly doped Si with Ag tip 33 was also not observed in the present study.…”

Superconductivity in silicon: a review

“…The superconducting phase was obtained with a considerable high T c 11 K and superconducting energy gap of 2 meV. 17 shown in figure 4. Subsequently, the superconducting phase under point contacts was examined on both n-doped (As dopants) and p-doped (B-dopants) facets of silicon crystals using various metallic tips exhibiting universal behavior of mesoscopic superconductivity in silicon crystals.…”

“…Recently, evidence of superconductivity was found in moderately doped silicon crystals under point contacts with non-superconducting metallic tips with reasonably high critical temperature(∼ 11K). 17 The superconducting phase was examined in As-doped Si (111) with the mean free path of electrons decide the transport regimes. 48 Ballistic transport regime is said to occur in the condition when the contact diameter becomes smaller than electron's elastic mean free path.…”

“…low temperatures and heavy doping beyond the solubility limit. 15,16 Recently, a superconducting phase in moderately doped crystalline silicon was studied under non-superconducting metallic point contacts depicting a high critical temperature of 11 K. 17 Besides the bulk form of silicon, it's different structural forms including silicene and nano-structured silicon have shown potential for superconducting applications with relatively higher transition temperatures. This review article provides an overview of theoretical and experimental investigations in the emerging field of superconductivity in different phases of silicon.…”