科研之友
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摘要
Ab initio calculations have been performed on hexagonal layers of M2O3 (M being several transition metals of the 5d series) sandwiched by a band insulator such as Al2O3 that provides the honeycomb lattice where the 5d electrons reside. This corundum-structure-based superlattice is a way to design a honeycomb lattice with transition metal cations avoiding the use of largely polar surfaces. We find that this system supports the presence of Dirac cones at the Fermi level that open up with the introduction of spin-orbit coupling at various fillings of the 5d band. The DFT calculations performed in this paper show that the 5d(5) situation is always a trivial insulator, whereas the 5d(8) filling presents topological insulating configurations which evolve into a trivial state with increasing tensile strain or on-site Coulomb potential U. However, LDA + U calculations show a stable antiferromagnetic solution for the 5d(8) case at every U value, which would break time reversal symmetry and could affect the topological properties of the system. We also discuss the similarities with the buckled honeycomb lattice obtained using perovskite (111) bilayers previously studied in literature, in particular for the 5d(5) and 5d(8) configurations. This paper provides some clues on the stability of topological phases using metal oxides in general.
- 出版日期2015-12-1
