Composition dependence of the oxygen isotope effect in Ba{sub 1{minus}{ital x}}K{sub {ital x}}BiO{sub 3}: Evidence for oxygen-mass dependence of the coupling constant
- Morris Research Inc., 1918 University Avenue, Berkeley, California 94704 (United States)
We report measurements of the oxygen isotope effect and temperature dependence of the penetration depth for high-{ital T}{sub {ital c}} superconductors Ba{sub 1{minus}{ital x}}K{sub {ital x}}BiO{sub 3} with {ital x}=0.45, 0.375, and 0.36. We find that, with the decrease of the K content, both the oxygen isotope exponent {alpha}{sub O}={minus}{ital d} ln{ital T}{sub {ital c}}/{ital d} ln{ital M}{sub O} and reduced energy gap {delta}=2{Delta}(0)/{ital k}{sub {ital B}}{ital T}{sub {ital c}} increase: {alpha}{sub O}=0.21{plus_minus}0.02, {delta}=4.0{plus_minus}0.2 for {ital x}=0.45; {alpha}{sub O}=0.26{plus_minus}0.02, {delta}=4.5{plus_minus}0.2 for {ital x}=0.375; {alpha}{sub O}=0.34{plus_minus}0.03, {delta}=4.8{plus_minus}0.2 for {ital x}=0.36. Our results can be explained by a picture in which the electron-phonon coupling constant is oxygen-mass dependent due to the anharmonicity of phonon modes and/or the breakdown of the Migdal adiabatic approximation.
- OSTI ID:
- 44588
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 18 Vol. 51; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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