Correlations among c/b, Tc, and Madelung potentials in the system of RBa2Cu3Ox superconductors

Shiow-Fon Tsay; Shou-Yih Wang; Lance Horng; T. J. Watson Yang

doi:10.1103/PhysRevB.40.9408

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Correlations among c/b, Tc, and Madelung potentials in the system of RBa2Cu3Ox superconductors

Shiow-Fon Tsay, Shou-Yih Wang, Lance Horng, T. J. Watson Yang

DOI 10.1103/PhysRevB.40.9408 · Physical Review B

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Abstract

We have observed a correlation between the lattice-constant ratio c/b and the superconducting transition temperature Tc in R-Be-Cu-O superconductors (where R is a rare-earth element). Madelung potentials and the bond length of Cu(1)-O(3) are calculated and correlated with the distribution of Tc over the various RBa2Cu3O7 superconductors. Further consideration of YBa2Cu3Ox with variable x of suitable oxygen content leads to an explanation of the correlation of decreasing c/b ratio with increasing Tc. A Coulomb-type ionic mechanism is therefore suggested so that shortening of the c axis and increased chain length provides (1) a channel of charge-transfer excitation from chain to Cu-O layers and (2) a long-range Coulomb interaction between the two Cu-O layers, both of which result in stronger coupling between the two Cu-O layers and higher Tc. .AE

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.	91.5	Pressure not reported	midpoint
SmBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	93.8	Pressure not reported	midpoint
EuBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	94.5	Pressure not reported	midpoint
GdBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	94.7	Pressure not reported	midpoint
DyBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	93	Pressure not reported	midpoint
HoBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	93.4	Pressure not reported	midpoint
ErBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	93.2	Pressure not reported	midpoint
TmBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90.5	Pressure not reported	midpoint
YbBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	midpoint