Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: Metal-Insulator Transition 2

TT 34.15: Vortrag

Donnerstag, 28. Februar 2008, 18:00–18:15, H 2053

Scanning tunneling microscopy and spectroscopy study of charge and orbital ordering transition in La_0.5Sr_1.5MnO₄ — •Grzegorz Urbanik^1,2, Paul Sass¹, Christian Hess¹, Torben Hänke¹, Bernd Büchner¹, Antoni Ciszewski², Pascal Reutler³, and Alexandre Revcolevschi³ — ¹Institute for Solid State Research, IFW-Dresden, 01171 Dresden, Germany — ²Institute of Experimental Physics, University of Wroclaw, 50-204 Wroclaw, Poland — ³Laboratoire de Physico-Chimie de l’Etat Solide, Université Paris Sud, Bâtiment 414, 91405 Orsay, France

The charge and orbital ordering compound La_0.5Sr_1.5MnO₄ has been studied by Scanning Tunneling Microscopy (STM) and Spectroscopy (STS). Cleaving of the crystal exposes flat surfaces on which atomically resolved topographic images are routinelly achieved above the charge ordering temperature T_CO≈225 K and below (down to T≈ 205 K). We have studied the temperature dependence of the electronic structure both for T>T_CO and T<T_CO. The temperature dependent STS clearly reveals finite DOS at the Fermi level for T>T_CO and the opening of a gap Δ≈0.5 eV just below T_CO. In the topographic studies we find nanometer scale modulations with various periodicity and orientations. We compare these modulations with the inherent charge and orbital ordered state of this material.