c-axis oxygen in copper oxide superconductors

A. Manthiram; X. X. Tang; J. B. Goodenough

doi:10.1103/PhysRevB.42.138

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c-axis oxygen in copper oxide superconductors

A. Manthiram, X. X. Tang, J. B. Goodenough

DOI 10.1103/PhysRevB.42.138 · Physical Review B

T1

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Abstract

Exploration of the roles of c-axis oxygen in the copper-oxide superconductors has revealed a new type of tetragonal-orthorhombic transition in the system R2−zCezBa2−yLyCu3O8+x(R=Nd or Gd, L=La or Nd) and one probably due to cluster rotation in fluorinated La2−yDyyCuO4−xF2x having the T* structure with interstitial F ordered in the rocksalt layer. The former is due to c-axis ionic displacements that relieve a compressive stress on the (Ba,L)O rocksalt sheets, the latter a tensile stress on the LaO rocksalt sheets. In the YBa2Cu3O6+x structure, the c-axis oxygen participates in oxygen diffusion in the superconductively inactive layers, they act as gates for stabilizing holes in Cu(1)Ox planes versus CuO2 sheets, and they modulate the width W of the σx2-y2* conduction band. These modulations are shown to be capable of changing the bandwidth from W<U to W>U and hence to provide a rationalization for the nonsuperconducting metallic copper oxides containing copper in a formal valence state greater than 2+. As modulators of bandwidth, their displacements offer electron-lattice interactions for pairing superconductive holes. In the n-type superconductors, interstitial c-axis oxygen perturbs the σx2-y2* band so as to introduce localized states at the band edges that suppress superconductivity.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
R2-zCezBa2-yLyCu3O8+x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
La2-yDyyCuO4-xF2x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O6+x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown