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Title: Transport and microwave properties of YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] superconducting films

Abstract

High quality YBCO c-axis oriented films were made by a laser ablation technique. Josephson weak links were fabricated on a modified microbridge by using bicrystal YBCO films. Shapiro steps were observed on modified microbridge weak links. Vortex ring nucleation by thermal activation and quantum tunneling processes in high T[sub c] superconductors is discussed. The nonlinear resistance scales as e[sup [minus]](J[sub v]/J)[sup v]. Thermal activation yields a critical index of v = 1, while quantum tunneling (without normal current dissipation) yields v = 2. I-V characteristics were measured on both disordered (low J[sub c]), ordered (high J[sub c]) YBCO films and microbridges below T[sub c]. The data were examined in terms of both thermal activation and quantum tunneling models. Intrinsic critical current densities in high T[sub c] superconducting films are discussed. The enhancement of the quantum electrodynamic tunneling process due to normal current dissipation is proposed to explain the measured J[sub c] results for YBCO films. The limitation of J[sub c] appears to be due to vortex ring creation. Studying J[sub c] of bridge constrictions was a way to approach the depairing current limit. A novel microwave self-resonant (MSR) technique was developed to measure surface resistance, R[sub 8], of YBCO superconductingmore » films directly and surface reactance, X[sub 8], indirectly. R[sub 8] at 21 GHz decreased by about three orders of magnitude as the temperature decreased from 90K to 80K. The smallest surface resistance was 2.7 [times] 10[sup [minus]4][Omega] at 21 GHz and at 15K, and the surface reactance was 0.031[Omega]. Using the MSR technique, the authors measured the London penetration depth and coherence length, and found that both [lambda] and [xi] were anisotropic, their values depended on the direction of the microwave electric field relative to the c-axis.« less

Authors:
Publication Date:
Research Org.:
Northeastern Univ., Boston, MA (United States)
OSTI Identifier:
7303107
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SUPERCONDUCTING FILMS; ELECTRICAL PROPERTIES; TUNNEL EFFECT; BARIUM OXIDES; CUPRATES; CURRENT DENSITY; ELECTRIC BRIDGES; ELECTRIC CONDUCTIVITY; HIGH-TC SUPERCONDUCTORS; INTERMETALLIC COMPOUNDS; JOSEPHSON JUNCTIONS; MICROWAVE RADIATION; YTTRIUM OXIDES; ALKALINE EARTH METAL COMPOUNDS; ALLOYS; BARIUM COMPOUNDS; CHALCOGENIDES; COPPER COMPOUNDS; ELECTRICAL EQUIPMENT; ELECTROMAGNETIC RADIATION; EQUIPMENT; FILMS; JUNCTIONS; OXIDES; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES; RADIATIONS; SUPERCONDUCTING JUNCTIONS; SUPERCONDUCTORS; TRANSITION ELEMENT COMPOUNDS; YTTRIUM COMPOUNDS; 360207* - Ceramics, Cermets, & Refractories- Superconducting Properties- (1992-)

Citation Formats

Jiang, H. Transport and microwave properties of YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] superconducting films. United States: N. p., 1992. Web.
Jiang, H. Transport and microwave properties of YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] superconducting films. United States.
Jiang, H. 1992. "Transport and microwave properties of YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] superconducting films". United States.
@article{osti_7303107,
title = {Transport and microwave properties of YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] superconducting films},
author = {Jiang, H},
abstractNote = {High quality YBCO c-axis oriented films were made by a laser ablation technique. Josephson weak links were fabricated on a modified microbridge by using bicrystal YBCO films. Shapiro steps were observed on modified microbridge weak links. Vortex ring nucleation by thermal activation and quantum tunneling processes in high T[sub c] superconductors is discussed. The nonlinear resistance scales as e[sup [minus]](J[sub v]/J)[sup v]. Thermal activation yields a critical index of v = 1, while quantum tunneling (without normal current dissipation) yields v = 2. I-V characteristics were measured on both disordered (low J[sub c]), ordered (high J[sub c]) YBCO films and microbridges below T[sub c]. The data were examined in terms of both thermal activation and quantum tunneling models. Intrinsic critical current densities in high T[sub c] superconducting films are discussed. The enhancement of the quantum electrodynamic tunneling process due to normal current dissipation is proposed to explain the measured J[sub c] results for YBCO films. The limitation of J[sub c] appears to be due to vortex ring creation. Studying J[sub c] of bridge constrictions was a way to approach the depairing current limit. A novel microwave self-resonant (MSR) technique was developed to measure surface resistance, R[sub 8], of YBCO superconducting films directly and surface reactance, X[sub 8], indirectly. R[sub 8] at 21 GHz decreased by about three orders of magnitude as the temperature decreased from 90K to 80K. The smallest surface resistance was 2.7 [times] 10[sup [minus]4][Omega] at 21 GHz and at 15K, and the surface reactance was 0.031[Omega]. Using the MSR technique, the authors measured the London penetration depth and coherence length, and found that both [lambda] and [xi] were anisotropic, their values depended on the direction of the microwave electric field relative to the c-axis.},
doi = {},
url = {https://www.osti.gov/biblio/7303107}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1992},
month = {1}
}

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