Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 31: Correlated Electrons: Low-Dimensional Systems -Materials 1

TT 31.9: Talk

Tuesday, March 12, 2013, 11:45–12:00, H41

Modelling random oxygen defects and magnetism at titanate interfaces — •Natalia Pavlenko^1,2, Thilo Kopp¹, G.A. Sawatzky³, and J. Mannhart² — ¹EKM und Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany — ²Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany — ³Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada V6T1Z1

We analyze the magnetic state at the LaAlO₃/SrTiO₃ (LAO/STO) interface within density unctional theory and provide evidence that it depends strongly on the oxidation state of the interfaces. We show that oxygen defects at titanate interfaces induce a complex multiorbital reconstruction which involves a lowering of the local symmetry and an inversion of t_2g and e_g orbitals resulting in the occupation of the eg orbitals of Ti atoms neighboring the O-defects. In contrast to stoichiometric nonmagnetic interfaces of LaAlO₃ and SrTiO₃, the defect-induced orbital reconstruction at LAO/STO interfaces generates a two-dimensional interface magnetic state not observed in bulk SrTiO₃. Using an effective two-band Hubbard model with disorder, we analyze the stability of the 2d-magnetic states at titanate interface for different concentrations of random defects.