The high temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}: symmetry of the order parameter, and gradiometers for biomagnetic applications

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The cuprate YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} is the material that drives the majority of the technological applications of high transition temperature ({Tc}) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-{Tc} superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-{Tc} superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting ... continued below

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Kouznetsov, Konstantin A. December 1, 1999.

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The cuprate YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} is the material that drives the majority of the technological applications of high transition temperature ({Tc}) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-{Tc} superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-{Tc} superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa{sub 2}C u{sub 3}O{sub 7{minus}{delta}}. A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} in superconducting electronics. The authors introduce a novel Superconducting Quantum Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T{sub c} SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the pickup up loop of a directly coupled magnetometer. T he long baseline of the gradiometer, 48 mm, and the intrinsic. Balance of better than 1 part in 100 make it an ideal candidate for operation in biomagnetic systems in an unshielded environment. They demonstrate a practical multichannel SQUID system for MagnetoCardioGraphy. Using this system, they are able to detect magnetic signals from the human heart in an unshielded environment, thereby demonstrating the applicability of their technology to practical applications. Their gradiometers are readily manufacturable devices that could be used in clinical applications in the near future.

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Medium: P; Size: 120 pages

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INIS; OSTI as DE00753117

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  • Other Information: TH: Thesis (Ph.D.); Submitted to Univ. of California, Berkeley, CA (US); Supercedes report DE00753117

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  • Report No.: LBNL--44865
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 753117
  • Archival Resource Key: ark:/67531/metadc709301

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • December 1, 1999

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  • Sept. 12, 2015, 6:31 a.m.

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  • April 5, 2016, 5:11 p.m.

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Kouznetsov, Konstantin A. The high temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}: symmetry of the order parameter, and gradiometers for biomagnetic applications, thesis or dissertation, December 1, 1999; California. (digital.library.unt.edu/ark:/67531/metadc709301/: accessed October 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.