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Charge transfer in high-{ital T}{sub {ital c}} superconducting superlattices

Journal Article · · Physical Review, B: Condensed Matter
;  [1]
  1. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6032 (United States)
A previously developed model of charge transfer in YBa{sub 2}Cu{sub 3}O{sub 7}/PrBa{sub 2}Cu{sub 3}O{sub 7} (YBCO-PBCO) superlattices is described in detail, refinements of the approach are discussed, and extensions are made to barrier layers other than PBCO, e.g., Pr{sub 0.7}Y{sub 0.3}Ba{sub 2}Cu{sub 3}O{sub 7} and Pr{sub 0.5}Ca{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7}. An expression for the energy of a supercell as a function of the charges transferred from the barrier layers to the YBCO is set up and minimized subject to the constraint of charge neutrality of the supercell. The approximate distribution of the transferred charge between the chain and CuO{sub 2} plane regions within a given YBCO unit cell is found by invoking symmetry arguments and results from Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7} alloys. The dependence of the superconducting transition temperature on the hole density in the CuO{sub 2} planes is taken from a spin-polaron theory of high-{ital T}{sub {ital c}} superconductivity which gives a good fit to the experimentally measured {ital T}{sub {ital c}}({ital x}) function in bulk YBCO and La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4}. Satisfactory agreement with the measured {ital T}{sub {ital c}} values at the midpoint of the resistive transition region for a variety of YBCO superlattices is found. Experimental evidence in support of charge transfer as the main mechanism determining {ital T}{sub {ital c}} is cited. It is emphasized that pairing interactions between YBCO unit cells are not the origin of high-{ital T}{sub {ital c}} superconductivity in these materials.
Research Organization:
Oak Ridge National Laboratory
DOE Contract Number:
AC05-84OR21400
OSTI ID:
44543
Journal Information:
Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 17 Vol. 51; ISSN 0163-1829; ISSN PRBMDO
Country of Publication:
United States
Language:
English