Abstract
Under the density functional theory framework, we have calculated the electronic and elastic properties of APoO3 (A = Be, Mg, Ca, Sr, Ba, and Ra) cubic perovskites. We found that CaPoO3, SrPoO3, BaPoO3, and RaPoO3 are topological insulators (TIs) with very large bandgaps of 0.861, 0.871, 0.820, and 0.810 eV, respectively. The nontrivial band topology together with the Z2 topological number of APoO3 perovskite are investigated. We also theoretically determine the three independent elastic constants C11, C12, and C44 of the APoO3 perovskite. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and anisotropy factor are also calculated from the obtained elastic constants. We found that the Debye temperature for the APoO3 perovskite is around 330-370 K. In the bulk APoO3 perovskite, if the center Po atom is shifted 0.09Å away from the center, the induced electric polarization is quite large, being around 0.02 C/m2. In the surface band calculation, we found that both AO and PoO2 surfaces give rise to contributions to the conduction channel. If the Po atom moves both in-plane and out-of-plane, we show that both electric polarization and topologically protect surface conduction states exist in APoO3 perovskite, indicating that these oxide APoO3 perovskites are ferroelectric TIs and might be useful for spintronic applications.
Highlights
Topological insulators [1,2], which are characterized by an insulating bulk state and a unique protected gapless surface state, have been of particular interest in the past decades.Topological insulators are a new kind of material that have attracted much attention due to their interesting properties and great potential for spintronic devices [3,4]
Without the spin-orbit coupling effect, we found that all APoO3 perovskites were ordinary metals
We found that CaPoO3, SrPoO3, BaPoO3, and RaPoO3 were possible topological insulators
Summary
Topological insulators are a new kind of material that have attracted much attention due to their interesting properties and great potential for spintronic devices [3,4]. The metallic surface states of the TIs are linearly dispersed in the momentum space with the helical spin textures that are protected by time-reversal symmetry and are characterized by the so-called Z2 topological invariant [5]. These interesting features have increased the interest in TIs for scientists in both experimental and theoretical [6] research fields. TI phase itself is interesting, but the combination with other physical properties or phases, such as superconductivity and magnetism [8,9], is promising
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