Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.37: Poster

Wednesday, March 28, 2012, 15:00–19:00, Poster B

Charge carrier density at the (Na/K)TaO₃/SrTiO₃ interfaces — •Udo Schwingenschlögl and Safdar Nazir — KAUST, PSE Division, Thuwal 23955-6900, Kingdom of Saudi Arabia

The formation of a quasi two-dimensional electron gas between the band insulators NaTaO₃ and SrTiO₃ as well as KTaO₃ and SrTiO₃ is studied by means of the full-potential linearized augmented plane-wave method of density functional theory. Optimization of the atomic positions points to only small changes in the chemical bonding at the interface. The creation of metallic interface states thus is not affected by structural relaxation but can be explained by charge transfer between transition metal and oxygen atoms. It is to be expected that a charge transfer is likewise important for related interfaces such as LaAlO₃/SrTiO₃. Both the p-type (NaO)⁻/(TiO₂)⁰ and n-type (TaO₂)⁺/(SrO)⁰ interfaces in NaTaO₃/SrTiO₃ are found to be metallic with strongly enhanced charge carrier densities as compared to the respective interfaces in KTaO₃/SrTiO₃. The effects of O vacancies are discussed. Spin-polarized calculations point to the formation of isolated O 2p magnetic moments, located in the metallic region of the p-type interface. The systems under investigation are suitable for disentangling the complex behavior of metallic interface states, since the structural relaxation is small.