Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 22.5: Vortrag

Mittwoch, 28. März 2012, 10:30–10:45, H 0104

Confinement induced metal-to-insulator transition in strained LaNiO₃/LaAlO₃ superlattices — •Arianda Blanca-Romero and Rossitza Pentcheva — Ludwig Maximilians University, Munich, Germany.

Using density functional theory calculations including a Hubbard U term we explore the effect of strain and confinement on the electronic ground state of superlattices containing the band insulator LaAlO₃ and the correlated metal LaNiO₃. Besides a suppression of holes at the apical oxygen, a central feature is the asymmetric response to strain in single unit cell superlattices: For tensile strain a band gap opens due to charge disproportionation at the Ni sites with two distinct magnetic moments of 1.45µ_B and 0.71µ_B. Under compressive stain, charge disproportionation is nearly quenched and the band gap collapses due to overlap of d_3z²−r² bands through a semimetallic state. This asymmetry in the electronic behavior is associated with the difference in octahedral distortions and rotations under tensile and compressive strain. The ligand hole density and the metallic state are quickly restored with increasing thickness of the (LaAlO₃)_n/(LaNiO₃)_n superlattice from n=1 to n=3.
Funding by DFG within SFB/TR80 is gratefully acknowledged.