Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme

TT 30.42: Poster

Donnerstag, 11. März 2004, 14:30–19:00, Poster A

In-plane infrared conductivity of untwinned La_2−xSr_xCuO₄ crystals in the regime of stripe order. — •Michael Dumm^1,2, Dimitri Basov², Seiki Komiya³, and Yoichi Ando³ — ¹1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart — ²Department of Physics, University of California at San Diego, La Jolla, CA, USA — ³Central Research Institute of Electric Power Industry, Tokyo, Japan

Using infrared spectroscopy, we show that spin self-organization in untwinned La_1.97Sr_0.03CuO₄ and La_1.96Sr_0.04CuO₄ single crystals has profound consequences for the dynamical conductivity σ(ω). The electronic response of CuO₂ planes acquires significant anisotropy in the spin-ordered state with enhancement of the conductivity along the direction of the diagonal spin stripes by up to a factor of two. An examination of the anisotropic response indicates that the diagonal spin texture in weakly doped La_2−xSr_xCuO₄ is also accompanied by the modulation of charge density. The electronic response of the charge stripes is found to be gapless consistent with the hypothesis of the metallic ground state. Our experiments directly show that the striped ordered systems reveal new degrees of freedom not present in ordinary one-dimensional conductors.