Dresden 2009 – wissenschaftliches Programm
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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).