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Pentcheva, Rossitza; Pickett, Warren E. (2008): Ionic relaxation contribution to the electronic reconstruction at the n-type LaAlO(3)/SrTiO(3) interface. In: Physical Review B, Vol. 78, No. 20
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Density-functional theory calculations reveal that the compensationmechanism at the isolated n-type interface in LaAlO(3)/SrTiO(3)superlattices involves both ionic and electronic degrees of freedom.Strong polar distortions screen the local electric field and reduce theband discontinuity across the interface. We find that the electronicreconstruction depends sensitively on whether structural optimization isperformed within GGA (conventional exchange and correlation effects) orGGA+U (which includes strong intra-atomic interactions). For astructural optimization within GGA+U the excess charge is confined tothe interface TiO(2) layer with a charge-ordered, orbitally polarizedarrangement of Ti(3+) and Ti(4+). While the charge-ordered phaserepresents the ground state, optimization within GGA leads to morepronounced lattice polarization, suppression of charge order (withremaining d(xy)-orbital occupation in the interface layer), and adelocalization of the excess charge extending over a few SrTiO(3)layers.