American Physical Society
We have performed both Josephson and quasiparticle tunneling in vacuum tunnel junctions formed between a conventional superconducting scanning tunneling microscope tip and overdoped Bi2Sr2CaCu2O8+δ single crystals. A Josephson current is observed with a peak centered at a small finite voltage due to the thermal-fluctuation-dominated superconducting phase dynamics. Josephson measurements at different surface locations yield local values for the Josephson IcRn product. Corresponding energy gap measurements were also performed and a surprising inverse correlation was observed between the local IcRn product and the local energy gap.
Hikari Kimura, R. P. Barber, Jr., S. Ono, Yoichi Ando and R. C. Dynes, "Scanning Josephson Tunneling Microscopy of Single Crystal Bi2Sr2CaCu2O8+δ with a Conventional Superconducting Tip," Physical Review Letters, 101, 037002 (2008).