Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 30: Superconductivity: Twenty Years High-T_c Cuprates - Recent Progress

TT 30.3: Vortrag

Donnerstag, 30. März 2006, 14:30–14:45, HSZ 02

Charge and spin ordering phenomena in HTSC — •Leonardo Tassini, Wolfgang Prestel, Rudi Hackl, Michael Lambacher, and Andreas Erb — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany

We present a detailed study of the underdoped range of the phase diagram of various single crystals of La_2−xSr_xCuO₄ (LSCO) and of Y_1−xCa_xBa₂Cu₃O₆ (YBCO) using electronic Raman scattering. We conclude from the experimental data that there is a clear indication of a charge and/or spin modulation (stripes) in the two-dimensional CuO₂ planes manifesting themselves as additional Drude-like peaks at low energies and temperatures. The additional response in LSCO is in the B_2g and B_1g symmetry at doping levels of x=0.02 and x=0.10, respectively, and in the B_2g symmetry for all YBCO samples studied. The selection rules allow us to determine the orientation of the stripes to be along the diagonal of the CuO₂ plane in YBCO and in LSCO at x=0.02, and along the principle axes in LSCO at x=0.10. The stripes fluctuate, and the correlation length is of the order of the electronic mean free path. In LSCO temperature is the only scale of the response at different doping levels demonstrating the importance of quantum critical behaviour.

This work is supported by the Deutsche Forschungsgemeinschaft (Research unit 538).