The crystalline electric field as a direct probe for charge transfer processes in high-temperature superconductors (abstract) : 35th annual conference on magnetism and magnetic materials

1089-7550

AIP Digital Archive

Physics

Charge fluctuations and charge transfer processes appear to be important mechanisms towards understanding high-Tc superconductivity.1 We describe the inelastic-neutron-scattering technique to observe the crystalline electric field (CEF) as a direct probe of the local symmetry and charge distribution at the rare-earth site. For RBa2Cu3Ox (R=Ho,Er; 6〈×〈7) we have succeeded to directly prove the oxygen-vacancy-induced charge redistribution in the CuO2 planes,2,3 which support the idea of charge transfer from the chains to the planes.4 An empirical relation between Tc and the observed charge transfer Δρ3 is derived which is highly nonlinear close to Tc=90 K.3 Charge transfer can also be realized by pressure and doping (at the Cu sites). Neutron spectroscopic CEF studies performed under pressure up to 10 kbar and with doped systems RBa2Cu3−xMxO7 (M=Ni,Zn) as well as CEF studies on RBa2Cu4O8 compounds can be consistently described within our picture. Similarly, we have analyzed the neutron spectroscopic data available for the recently discovered high-Tc cuprates Nd2−xCexCuO4 and found direct evidence for the electron doping process occurring in the copper-oxide planes.〈ks〉

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