Anomalous oxygen isotope effect in La sub 2 minus x Sr sub x CuO sub 4

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.282· OSTI ID:6963770

Crawford, M K ^[1]; Kunchur, M N ^[2]; Farneth, W E; McCarron, III, E M ^[1]; Poon, S J ^[2]

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1. E. I. Du Pont de Nemours and Co., Inc., Central Research and Development Department, Experimental Station, Wilmington, Delaware 19880-0356 (USA)
2. Department of Physics, University of Virginia, Charlottesville, Virginia 22901 (USA)

We report measurement of the oxygen isotope effect {alpha}{sub O} in La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4} as a function of {ital x}. For values of {ital x}{lt}0.15, {alpha}{sub O} in the expression {ital T}{sub {ital c}}{similar to}M{sup {minus}{alpha}{sub O}} is large (0.4--0.6) but decreases by about a factor of 5 for {ital x}{ge}0.15, where we obtain {alpha}{sub O}{approx}0.1, in good agreement with earlier results. The large values of {alpha}{sub O} obtained for small {ital x} are reproducible when the {sup 18}O,{sup 16}O sample pairs are cross exchanged. The maximum measured values of {alpha}{sub O} fall outside the range of standard Bardeen-Cooper-Schrieffer theory and may imply anharmonic phonon-mediated superconductivity. The variability of {alpha}{sub O} may be related to a nearby lattice instability, similar to that observed in (La,Ba){sub 2}CuO{sub 4}. Isotope frequency shifts of the far-infrared transverse-optic phonons of {ital A}{sub 2{ital u}} symmetry at 240 and 500 cm{sup {minus}1} also display an anomaly between {ital x}=0.11 and 0.15 and, in addition, demonstrate {sup 18}O exchange for both oxygen sites.

• OSTI ID: 6963770
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:1; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EVEN-EVEN NUCLEI
ISOTOPE EFFECTS
ISOTOPES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LIGHT NUCLEI
MINERALS
NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PEROVSKITE
PEROVSKITES
PHONONS
PHYSICAL PROPERTIES
QUANTITY RATIO
QUASI PARTICLES
RARE EARTH COMPOUNDS
STABILITY
STABLE ISOTOPES
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS