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Anomalous proximity effect in underdoped YBa2Cu3O6+x josephson junctions
1Laboratory 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.
Physical Review Letters
|October 13, 2000
Summary
Researchers photogenerated Josephson junctions in YBa2Cu3O6+x films, revealing a large proximity effect and perturbing insulating material into a superconducting state. This challenges existing theories for high-temperature superconductors.
Area of Science:
- Condensed matter physics
- Materials science
- Superconductivity
Background:
- High-temperature superconductors, specifically the YBa2Cu3O6+x family, exhibit complex phase diagrams.
- Understanding the interplay between superconducting and insulating states is crucial for these materials.
Purpose of the Study:
- To investigate the properties of Josephson junctions in underdoped YBa2Cu3O6+x thin films.
- To explore the proximity effect in these materials and its implications for superconductivity.
Main Methods:
- Photogeneration of Josephson junctions using a near-field scanning optical microscope.
- Measurement of the Josephson effect and critical current.
Main Results:
- Josephson junctions were successfully created in underdoped YBa2Cu3O6+x films.
- An anomalously large proximity effect was observed, with Josephson effects seen up to 100 nm separations.
- Insulating material within the junction gap was readily perturbed into a superconducting state.
- Critical current measurements were consistent with the conventional Josephson relationship.
Conclusions:
- The findings demonstrate a significant proximity effect in underdoped cuprates.
- The results suggest that the insulating regions in these superconductors can be induced into a superconducting state.
- The observed phenomena may constrain the applicability of SO(5) theory for explaining the phase diagram of high-temperature superconductors.