O. Naaman et al., Fluctuation dominated Josephson tunneling with a scanning tunneling microscope - art. no. 097004, PHYS REV L, 8709(9), 2001, pp. 7004
We demonstrate Josephson tunneling in vacuum tunnel junctions formed betwee
n a superconducting scanning tunneling microscope tip and a Pb film, for ju
nction resistances in the range 50-300 k Omega. We show that the supercondu
cting phase dynamics is dominated by thermal fluctuations, and that the Jos
ephson current appears as a peak centered at small finite voltage. In the p
resence of microwave fields (f = 15.0 GHz) the peak decreases in magnitude
and shifts to higher voltages with increasing rf power, in agreement with t
heory.