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Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 22: Low-dimensional Systems - Materials

TT 22.6: Talk

Thursday, March 29, 2007, 10:45–11:00, H18

Correlation driven charge order at LaAlO3/SrTiO3 and LaTiO3/SrTiO3 Interfaces — •Rossitza Pentcheva1 and Warren Pickett21Section Crystallography, Dept. of Earth and Environmental — 2Department of Physics, University of California, Davis,

To explain recent experiments reporting metallic conductivity at the interfaces between the Mott insulator LaTiO3 (LTO) and band insulator SrTiO3 (STO) but also between the two simple band insulators LaAlO3 (LAO) and STO we have performed density-functional theory calculations employing the FP-LAPW-method within the WIEN2k implementation including a Hubbard-type on site Coulomb repulsion (DFT+U). We find that charge mismatch at the LTO/STO IF is accommodated by the formation of a charge and orbitally ordered (CO/OO) layer with a checkerboard arrangement of Ti3+ and Ti4+ and an antiferromagnetic coupling of the Ti3+-spins [1]. Lattice relaxations lead to the observed conducting behavior. An analogous diluted layer of Ti3+ spins is obtained for the n-type LAO/STO interface, although the corresponding bulk materials are nonmagnetic [2]. For a structurally ideal p-type LAO/STO IF strong correlations in the oxygen p states and the formation of a charge and orbitally ordered O Pπ magnetic hole render a possible explanation for the measured insulating behavior. Alternatively, charge compensation by oxygen vacancies and the formation of a charge conjugate F-center is considered.

[1] R. Pentcheva and W.E. Pickett, cond-mat/0608212.

[2] R. Pentcheva and W.E. Pickett, Phys. Rev. B. 74, 035112 (2006).

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