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Studies of the microwaves surface resistance of pure, zinc, and nickel doped YBCO crystals Zhang, Kuan
Abstract
An apparatus utilizing a superconducting cavity resonator has been developed for the systematic study of the microwave surface resistance of high purity (twinned and untwinned), zinc and nickel doped YBa₂Cu₃O₇₋₈ single crystals at 35 GHz. The objective was to obtain the intrinsic microwave properties of high temperature superconductors. By using our highly sensitive apparatus to study the effects of twinning and doping, we have been able to confirm that what we have obtained is indeed the intrinsic properties of YBa₂Cu₃O₇₋₈. The results show that the intrinsic microwave properties of YBa₂Cu₃O₇₋₈ are very different from that of conventional s-wave BCS superconductors. Firstly, the quasiparticle scattering rate is strongly temperature dependent, and drops rapidly below the transition temperature, which implies a quasiparticle-quasiparticle scattering mechanism. Secondly, both the surface resistance and the real part of the conductivity vary linearly with T below 35K (except for the zinc doped crystals), suggesting an unconventional superconducting pairing state with line nodes in the order parameter. Thirdly, the real part of the conductivity when extrapolated to the OK is very small, in contrast to previously existing data, and approaches the limit predicted for a d-wave superconductor. A practical result of our studies is that we have shown that the microwave loss of high temperature superconductors can be reduced by doping with certain impurities. This is an important result in the area of microwave applications, where one generally wants as low a surface resistance as possible
Item Metadata
| Title |
Studies of the microwaves surface resistance of pure, zinc, and nickel doped YBCO crystals
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| Creator | |
| Publisher |
University of British Columbia
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| Date Issued |
1995
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| Description |
An apparatus utilizing a superconducting cavity resonator has been developed for the systematic study of the microwave surface resistance of high purity (twinned and untwinned), zinc and nickel doped YBa₂Cu₃O₇₋₈ single crystals at 35 GHz. The objective was to obtain the intrinsic microwave properties of high temperature superconductors. By using our highly sensitive apparatus to study the effects of twinning and doping, we have been able to confirm that what we have obtained is indeed the intrinsic properties of YBa₂Cu₃O₇₋₈. The results show that the intrinsic microwave properties of YBa₂Cu₃O₇₋₈ are very different from that of conventional s-wave BCS superconductors. Firstly, the quasiparticle scattering rate is strongly temperature dependent, and drops rapidly below the transition temperature, which implies a quasiparticle-quasiparticle scattering mechanism. Secondly, both the surface resistance and the real part of the conductivity vary linearly with T below 35K (except for the zinc doped crystals), suggesting an unconventional superconducting pairing state with line nodes in the order parameter. Thirdly, the real part of the conductivity when extrapolated to the OK is very small, in contrast to previously existing data, and approaches the limit predicted for a d-wave superconductor. A practical result of our studies is that we have shown that the microwave loss of high temperature superconductors can be reduced by doping with certain impurities. This is an important result in the area of microwave applications, where one generally wants as low a surface resistance as possible
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| Extent |
3247003 bytes
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| Genre | |
| Type | |
| File Format |
application/pdf
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| Language |
eng
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| Date Available |
2009-04-22
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| Provider |
Vancouver : University of British Columbia Library
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| Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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| DOI |
10.14288/1.0085492
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| URI | |
| Degree | |
| Program | |
| Affiliation | |
| Degree Grantor |
University of British Columbia
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| Graduation Date |
1995-11
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| Campus | |
| Scholarly Level |
Graduate
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| Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.