Anomalous superconducting state gap size versus {ital T}{sub {ital c}} behavior in underdoped Bi{sub 2}Sr{sub 2}Ca{sub 1{minus}{ital x}}Dy{sub {ital x}}Cu{sub 2}O{sub 8+{delta}}
- Department of Applied Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305-4045 (United States)
- Ginzton Research Center, Varian Associates, Palo Alto, California 94304-1025 (United States)
We report angle-resolved photoemission spectroscopy measurements of the excitation gap in underdoped superconducting thin films of Bi{sub 2}Sr{sub 2}Ca{sub 1{minus}{ital x}}Dy{sub {ital x}}Cu{sub 2}O{sub 8+{delta}}. As {ital T}{sub {ital c}} is reduced by a factor of 2 by underdoping, the superconducting state gap {Delta} does not fall proportionally, but instead stays constant or increases slightly, in violation of the BCS mean-field theory result. The different doping dependences of {Delta} and {ital kT}{sub {ital c}} indicate that they represent different energy scales. The measurements also show that {Delta} is highly anisotropic and consistent with a {ital d}{sub {ital x}{sup 2}{minus}{ital y}{sup 2}} order parameter, as in previous studies of samples with higher dopings. However, in these underdoped samples, the anisotropic gap persists well above {ital T}{sub {ital c}}. The existence of a normal state gap is related to the failure of {Delta} to scale with {ital T}{sub {ital c}} in theoretical models that predict pairing without phase coherence above {ital T}{sub {ital c}}. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 399848
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 22 Vol. 54; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BISMUTH OXIDES
CALCIUM OXIDES
COPPER OXIDES
DYSPROSIUM OXIDES
ELECTRONIC STRUCTURE
ENERGY GAP
HIGH-TC SUPERCONDUCTORS
PAIRING INTERACTIONS
PHOTOEMISSION
QUASI PARTICLES
STRONTIUM OXIDES
SUPERCONDUCTING FILMS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
THIN FILMS
TRANSITION TEMPERATURE