Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 22: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 22.3: Talk

Wednesday, March 28, 2012, 10:00–10:15, H 0104

Magnetism and superconductivity at LAO/STO-interfaces: the role of Ti 3d interface electrons — •Natalia Pavlenko¹, Thilo Kopp¹, Evgeny Tsymbal², George Sawatzky³, and Jochen Mahhnart⁴ — ¹EKM and Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany — ²Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA — ³Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada V6T1Z1 — ⁴Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany

Ferromagnetism and superconductivity are in most cases adverse. However, recent experiments reveal that they coexist at interfaces of LaAlO₃ and SrTiO₃. We analyze the ferromagnetic state within density functional theory and provide evidence that it is also generated by Ti 3d interface electrons, as is the two-dimensional electron liquid at the interface which gives rise to superconductivity. We demonstrate that oxygen vacancies in the TiO₂ interface layer enhance the tendency for ferromagetism considerably. This allows for the notion that areas with increased density of oxygen vacancies produce ferromagnetic puddles and account for the previous observation of a superparamagnetic behavior in the superconducting state.