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Calculation of the isotope effect in La/sub 2-//sub x/M/sub x/CuO/sub 4/ and YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/

Journal Article · · Phys. Rev. B: Condens. Matter; (United States)
We have calculated the transition temperature and the isotope shift for oxygen replacement for La/sub 2-//sub x/M/sub x/CuO/sub 4/ and YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/, based on the lattice-dynamical calculations of these compounds with shell models. It is found that the exeprimental value of T/sub c/ and the isotope shift ..delta..T/sub c/ for La/sub 2-//sub x/M/sub x/CuO/sub 4/ can be accounted for on the basis of McMillan's strong-coupling equation for T/sub c/, supporting the conclusion that La/sub 2-//sub x/M/sub x/CuO/sub 4/ is a strong-coupling BCS superconductor. In contrast, experimental values of T/sub c/ for YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/ cannot be obtained on this basis. It is argued that expression isotope shifts in terms of isotopic mass exponents ..cap alpha../sub i/ is not a useful procedure for these multi-ionic compounds.
Research Organization:
Physics Department, University of Texas, Austin, Texas 78712
OSTI ID:
6781733
Journal Information:
Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 38:10; ISSN PRBMD
Country of Publication:
United States
Language:
English