Avoiding the polarization catastrophe in LaAlO3 overlayers on SrTiO3(001) through polar distortion

A pronounced uniform polar distortion extending over several unit cells enables thin LaAlO3 overlayers on SrTiO3(001) to counteract the charge dipole and thereby neutralize the "polarization catastrophe" that is suggested by simple ion counting. This unanticipated mechanism, obtained from...

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Bibliographic Details
Published inPhysical review letters Vol. 102; no. 10; p. 107602
Main Authors Pentcheva, Rossitza, Pickett, Warren E
Format Journal Article
LanguageEnglish
Published United States 13.03.2009
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Summary:A pronounced uniform polar distortion extending over several unit cells enables thin LaAlO3 overlayers on SrTiO3(001) to counteract the charge dipole and thereby neutralize the "polarization catastrophe" that is suggested by simple ion counting. This unanticipated mechanism, obtained from density functional theory calculations, allows several unit cells of the LaAlO3 overlayer to remain insulating (hence, fully ionic). The band gap of the system, defined by occupied O 2p states at the surface and unoccupied Ti 3d states at the interface in some cases approximately 20 A distant, decreases with increasing thickness of the LaAlO3 film before an insulator-to-metal transition and a crossover to an electronic reconstruction occurs at around five monolayers of LaAlO3.
ISSN:0031-9007
DOI:10.1103/PhysRevLett.102.107602