Point contact junctions made from two pieces of MgB2 can be adjusted to exhibit either superconductor-insulator-superconductor (SIS) or superconductor-normal metal-superconductor (SNS) current-voltage characteristics. The SIS characteristics are in good agreement with the standard tunneling model for s-wave superconductors, and yield an energy gap of (2.02 +/- 0.08) meV. The SNS characteristics are in good agreement with the predictions of the resistively-shunted junction model. DC Superconducting QUantum Interference Devices made from two SNS junctions yield magnetic field noise as low as 35 fT/Hz^{1/2} at 19 K.
@article{arxiv.cond-mat/0107478,
title = {MgB2 tunnel junctions and 19 K low-noise dc superconducting quantum interference devices},
author = {Y. Zhang and D. Kinion and J. Chen and D. G. Hinks and G. W. Crabtree and John Clarke},
journal= {arXiv preprint arXiv:cond-mat/0107478},
year = {2009}
}