Probing single-crystalline YBa2Cu3O7 across the superconducting transition temperature by positron annihilation measurements
Udayan De, D. Sanyal, S. Chaudhuri, P. M. G. Nambissan, Th. Wolf, H. Wühl
DOI 10.1103/PhysRevB.62.14519 · Physical Review B
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Abstract
Shape parameter S determined from the Doppler broadening of the positron annihilation radiation line-shape measurement (DBPARL), gives the fraction of suitably defined low momentum electrons among the annihilating electrons. Since BCS pairing in momentum space is accepted for the so-called conventional superconductors, such studies of possible changes in the electron momentum distribution as a function of temperature across the superconducting transition in high-temperature superconductors (HTSC) may help clarify the yet unknown mechanism of superconducting pairing in HTSC. Our S vs T data at close intervals (down to 1 K) of temperature revealed one minimum at Tc in Bi-2212 pellets and two minima in the Tc region in (Bi,Pb)-2223 pellets, in addition to the somewhat better known steplike change at Tc. Similar DBPARL measurements presently on Y-123 single crystals show the S vs T minima in these as well as in previous (Bi,Pb)-2223 pellets to be at Tc and 0.95Tc. These observations can imply a redistribution of electron momentum similar to the better discussed charge redistribution.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 89.5 | Pressure not reported | onset |
| YBa2Cu3-xAlxOz Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 89.5 | Pressure not reported | onset |
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