Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 106: Complex Oxides: Bulk Properties, Surfaces and Interfaces (joint session TT/MA/KFM)

TT 106.5: Vortrag

Freitag, 16. März 2018, 10:30–10:45, H 0110

Confinement-driven electronic and topological phases in corundum-derived oxide honeycomb superlattices — •Okan Koeksal and Rossitza Pentcheva — Department of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg

On the basis of density functional theory calculations plus the Hubbard U interaction, we investigate electronic, magnetic and possibly topologically non-trivial phases in X₂O₃ honeycomb layers confined in the corundum structure α-Al₂O₃ (0001). Our results predict that the ground states for most of the systems of X=3d cations are trivial antiferromagnetic Mott insulators. If the symmetry of the two sublattices is imposed, the ferromagnetic phases of Ti, Mn, Co and Ni exhibit a characteristic set of four bands associated with the single occupation of e_g′ (Ti) and e_g (Mn, Co, Ni) states. Moreover, the Dirac point can be tuned to the Fermi level by strain and a significant anomalous Hall conductivity arises when spin-orbit coupling (SOC) is switched on. A particularly strong SOC effect is identified for X = Ti at a_Al2O3=4.81 Å accompanied by an unusually high orbital moment of -0.88 µ_B nearly quenching the spin moment of 1.01 µ_B. The emergence of this orbital magnetism makes the realization of Haldane’s model of spinless fermions possible. The extension of this work to the 4d and 5d series led to the identification of cases of high orbital moment (Os) or candidates for Chern insulators (CI), i.e. X = Tc and Pt with C=-2 and -1, depending on the Coulomb repulsion strength. Support by the DFG within CRC/TRR80, project G3 is gratefully acknowledged.