Subsequent projects
PD Dr. Rossitza Pentcheva
Ludwig-Maximilians-University of Munich
Fakultät für Geowissenschaften -
Geo- und Umweltwissenschaft - Kristallographie
Prof. Dr. Warren E. Pickett
University of California, Davis
Department of Physics
Computational Design of Topological Behavior in Digital Oxide Heterostructures from First Principles
In recent years, topological insulators (TI) with their protected edge states, and atomic layer-by-layer design of oxide interfaces with several unexpected and exotic electronic phases, have been two areas of great excitement and intense research. So far, the materials classes in these two areas of study have been largely disjoint, with most of the research on TIs concentrating on binary semiconductor phases with strong spin‐orbit coupling. Building on our successful research in the area of oxide interfaces, we aim to explore design principles for topological behavior in metal oxide nano¬structures, based on density functional theory calculations, also including effects of strong electronic correlation. Through systematic variation of structural patterns and chemical composition we aim to establish microscopic relationships between structure, electronic concentration, and electronic properties, and thereby gain fundamental understanding of their role of in the emergence of unusual electronic and magnetic phases.
Primary project: Computational Design of Complex Oxide Heterostructures as New Materials
Final Report
The BaCaTeC subsequent funding enabled visits and intensive discussions and collaboration between the two partners with special focus on the search and design of novel and topologically nontrivial phases in oxide superlattices hosting a honeycomb layer. Using density functional theory calculations including an on-site Coulomb repulsion term together with topological analysis based on the Berry curvature and anomalous Hall conductivity, a number of promising cases could be identified within the perovskite- and corundum-derived systems. In the former case of LaXO3 (111)-bilayers sandwiched between the band insulator LaAlO3, several representatives of the 3d series (e.g. X=Mn, Co, Ni) [1,2] show Dirac-like crossings at the Fermi level. Among those, a particularly strong spin-orbit effect was found for the LaMnO3(111) bilayer that opens a substantial gap and makes the system a Chern insulator, when the symmetry between the two honeycomb sublattices is preserved [2]. Symmetry breaking was found to quench the topological properties, nevertheless it leads to unexpected orbital reconstructions that are not found in the (001)-oriented superlattices. This systematic study served as basis to extend to corundum-derived systems [3] as well as to 4d and 5d cases [4-6] to gain a fundamental insight in the effect of band filling and interplay of electronic correlations and spin-orbit effects. Several collaborations with experimental groups working on the realization of these systems, have emerged out of this, e.g. [7,8].
[1] D. Doennig, W.E. Pickett and R. Pentcheva, Confinement-driven transitions between topological and Mott phases in (LaNiO3)N/(LaAlO3) M (111) superlattices, Phys. Rev. B 89, 121110(R) (2014).
[2] D. Doennig, S. Baidya, W.E. Pickett and R. Pentcheva, Design of Chern and Mott insulators in buckled 3d oxide honeycomb lattices,Phys. Rev. B 93, 165145 (2016).
[3] O. Köksal, S. Baidya, and R. Pentcheva, Confinement-driven electronic and topological phases in corundum-derived 3d-oxide honeycomb lattices, Phys. Rev. B 97, 035126 (2018).
[4] H. Guo, S. Gangopadhyay, O. Köksal, R. Pentcheva, and W. E. Pickett, Wide gap Chern Mott insulating phases achieved by design, npj Quantum Materials 2, 4 (2017).
[5] O. Köksal and R. Pentcheva, Interaction-driven spin-orbit effects and Chern insulating phases in corundum-based 4d and 5d oxide honeycomb lattices, J. Phys. Chem. Solids (Special Issue: Spin-Orbit Materials), 128, 301-309 (2019).
[6] O. Köksal and R. Pentcheva, Chern and Z(2) topological insulating phases in perovskite-derived 4d and 5d oxide buckled honeycomb lattices, Sci. Reports 9, 17306 (2019).
[7] S. Middey, D. Meyers, D. Doennig, M. Kareev, X. Liu, Y. Cao, Zhenzhong Yang, Jinan Shi, Lin Gu, P. J. Ryan, R. Pentcheva, J. W. Freeland, and J. Chakhalian, Mott Electrons in an Artificial Graphenelike Crystal of Rare-Earth Nickelate, Phys. Rev. Lett. 116, 056801 (2016).
[8] A. Arab, X. Liu, O. Köksal, W. Yang, R. U. Chandrasena1, S. Middey, M.-A. Husanu, Z. Yang, L. Gu, V. N. Strocov, T.-L. Lee, J. Minár, R. Pentcheva, J. Chakhalian, and A. X. Gray, Electronic structure of a graphene-like artificial crystal of NdNiO3, Nanolett. 19, 8311 (2019).