All-MgB2 Josephson tunnel junctions

TL;DR

This paper reports the first fabrication of all-MgB2 Josephson tunnel junctions using molecular beam epitaxy, demonstrating promising superconducting properties suitable for electronics around 20 K.

Contribution

It introduces the first all-MgB2 Josephson junctions with detailed fabrication and characterization, advancing MgB2's application in superconducting electronics.

Findings

Substantial superconducting current with IcRN ~ 0.8 mV at 4.2K

Well-defined superconducting gap of ~2.3 mV

Clear Fraunhofer patterns indicating uniform junctions

Abstract

Sandwich-type all-MgB2 Josephson tunnel junctions (MgB2/AlOx/MgB2) have been fabricated for the first time with as-grown MgB2 films formed by molecular beam epitaxy. The junctions exhibit substantial superconducting current (IcRN product ~ 0.8 mV at 4.2K), a well-defined superconducting gap (delta = ~2.3 mV), and clear Fraunhofer patterns. The superconducting gap voltage of delta agrees well with the smaller gap in the multi-gap scenario. The results demonstrate that MgB2 has great promise for superconducting electronics that can be operated at T ~ 20 K.