Planar oxygen-centered lattice instabilities in Tl-based high- temperature superconductors

✍ Scribed by J.Mustre de Leon; G.G. Li; S.D. Conradson; A.R. Bishop; M.A. Subramanian; I.D. Raistrick

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 408 KB
• Volume: 220
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)90927-x

✦ Synopsis

Analysis of the copper K-edge X-ray absorption finestructure on TI2Ba2CuO6, TI2Ba2CaCu2Os, and Tl2Bat.2Sro.sCuO6 indicates that the copper--equatorial oxygen local structure changes in the vicinity of the superconducting transition. These data also show that the radial distribution function for these bonds is complex with several oxygen positions relative to the copper, indicating that the local structure of the CuO2 planes differs significantly from the average crystal structure. These results suggest the presence of polarons in these planes, whose structure changes across the superconducting transition, and are thus coupled to the hole pairing states.

Although the role of the lattice in high-temperature superconductivity is still controversial, experimental support for strong lattice-hole coupling is found through changes in the local structure around the superconducting transition temperature, To, observed by ion channeling [ 1 ], pair distribution function (PDF) analysis of neutron diffraction [2], M~Sssbauer spectroscopy [3], resonant neutron absorption spectroscopy [4], neutron inelastic scattering [ 5 ], and X-ray absorption fine structure (XAFS) [6,7]. Manifestations of this coupling in the electronic structure have been shown by optical conductivity measurements [8]. Several theoretical models also predict the existence of local structural instabilities which can be associated with the superconducting transition [9-I 1 ].

Conventional crystallography provides an accurate description of the average crystal structure of high-temperature superconductors [12], but is rel-Also at