Anomalous proximity effect in underdoped YBa2Cu3O6+x josephson junctions
Josephson junctions were photogenerated in underdoped thin films of the YBa2Cu3O6+x family using a near-field scanning optical microscope. The observation of the Josephson effect for separations as large as 100 nm between two wires indicates the existence of an anomalously large proximity effect and shows that the underdoped insulating material in the gap of the junction is readily perturbed into the superconducting state. The critical current of the junctions was found to be consistent with the conventional Josephson relationship. This result appears to constrain the applicability of SO(5) theory to explain the phase diagram of high critical temperature superconductors.
Decca
RS
Laboratory for Physical Sciences and Department of Physics, University of Maryland, College Park, Maryland 20742 and Department of Physics, IUPUI, Indianapolis, 402 North Blackford Street, Indianapolis, Indiana 46202, USA.
Drew
HD
Osquiguil
E
Maiorov
B
Guimpel
J