Contrasting oxygen and copper isotope effects in YBa2Cu4O8 superconducting and normal states
G. V. M. Williams, D. J. Pringle, J. L. Tallon
DOI 10.1103/PhysRevB.61.R9257 · Physical Review B
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Abstract
We have used Raman, susceptibility, and 89Y NMR measurements on the YBa2Cu4O8 superconductor synthesized using pure 63Cu or 65Cu to investigate the oxygen and copper isotope effects in Tc and the normal-state pseudogap. We find no copper or oxygen isotope effects in the normal-state 89Y Knight shift for temperatures in excess of 150 K. There is a positive copper isotope effect in Tc and, for temperatures less than 150 K, a negative copper isotope effect in the normal-state 89Y Knight shift. This differs from the oxygen isotope effect which is positive for both Tc and the 89Y Knight shift below 150 K. These results indicate that the normal-state pseudogap may not originate from precursor superconducting pairing.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu4O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 81.6 | Pressure not reported | onset |
| YBa2Cu3O6.41 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 49.5 | Pressure not reported | unknown |
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 48 | Pressure not reported | unknown |
| Y0.6Pr0.4Ba2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | unknown |
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