Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 4: Symposium Superconducting Cuprates

TT 4.4: Fachvortrag

Freitag, 4. März 2005, 15:15–15:45, TU H104

Ordering Phenomena in Cuprates — •Rudi Hackl¹, Leonardo Tassini¹, Francesca Venturini², Andreas Erb¹, Naoki Kikugawa³, and Toshitsu Fujita³ — ¹Walther-Meissner-Institut, D-85748 Garching — ²Bruker BioSpin AG, CH-8117 Faellanden — ³ADSM, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan

We present results of Raman scattering experiments on hole doped cuprates with 0 ≤ p ≤ 0.26. Spectra were measured for temperatures between 4.2 and 330 K as a function of polarization. In all compounds a strong anisotropy of the transport properties develops for doping levels below approximately 0.21. In agreement with recent photoemission experiments electrons with momenta along the diagonal of the copper-oxygen plane always exhibit metallic dynamics except for p ≡ 0. In contrast, for electronsmoving along the principal axes a metal-insulator transition is found at x ≃ 0.21. In addition to this quite general phenomenon, a new type of low-temperature response is found at material-dependent doping levels in La_2−xSr_xCuO₄ and Y_0.97Ca_0.03Ba₂Cu₃O_6+x. Both the spectral shape and the selection rules provide strong evidence that the new low-energy response originates from the formation of fluctuating one-dimensional charge order. In La_2−xSr_xCuO₄ the lattice apparently helps to stabilze stripes making them visible in a Raman experiment at doping levels up to at least 0.10.