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O: Fachverband Oberflächenphysik

O 60: Post Deadline Session followed by Surface Science "get-together"

O 60.3: Vortrag

Donnerstag, 26. März 2009, 20:30–20:45, HSZ 02

Polar catastrophe and how thin LaAlO₃ films on SrTiO₃(001) deal with it — •Rossitza Pentcheva¹ and Warren E. Pickett² — ¹Dept. of Earth and Environmental Sciences, University of Munich — ²Dept. of Physics, University of California at Davis

Even at the interface of conventional band insulators polar discontinuities can drive novel electronic behaviour: An example is the two-dimensional electron gas [1] and thickness dependent switching from insulating to conducting behaviour [2] reported in thin LaAlO₃ films on a SrTiO₃(001)-substrate.

Density functional theory calculations reveal that a strong polar distortion creates the necessary screening and enables several unit cells of LaAlO₃ to sustain their ionic charges and remain insulating. However, the band gap of the system, defined by O 2p states at the surface and Ti 3d states at the interface decreases with each added LaAlO₃-layer, before an insulator-to-metal transition and a crossover to an electronic reconstruction (as observed previously at the isolated interface [3]) takes place at around 5 monolayers of LaAlO₃. The implications of two different, spatially separated types of carriers - holes at the surface and electrons at the interface - will be discussed.

A BaCaTec grant and a computational grant at the Leibniz Rechenzentrum are gratefully acknowledged.

[1] A.Ohtomo and H.Y.Hwang, Nature 427, 423 (2004)

[2] S.Thiel et al., Science 313, 1942 (2006)

[3] R. Pentcheva and W.E. Pickett, Phys. Rev. B. 74, 035112 (2006); ibid. 78, 205106 (2008).