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The Enabling Electronic Motif for Topological Insulation in ABO(3) Perovskites

机译:用于ABO(3)钙钛矿中拓扑绝缘的启用电子图形。

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Stable oxide topological insulators (TIs) have been sought for years, but none have been found; whereas heavier (selenides, tellurides) chalcogenides can be TIs. The basic contradiction between topological insulation and thermodynamic stability is pointed out, offering a narrow window of opportunity. The electronic motif is first identified and can achieve topological band inversion in ABO(3) as a lone-pair, electron-rich B atom (e.g., Te, I, Bi) at the octahedral site. Then, twelve ABO3 compounds are designed in the assumed cubic perovskite structure, which satisfy this electronic motif and are indeed found by density function theory calculations to be TIs. Next, it is illustrated that poorly screened ionic oxides with large inversion energies undergo energy-lowering atomic distortions that destabilize the cubic TI phase and remove band inversion. The coexistence windows of topological band inversion and structure stability can nevertheless be expanded under moderate pressures (15 and 35 GPa, respectively, for BaTeO3 and RbIO3). This study traces the principles needed to design stable oxide topological insulators at ambient pressures as a) a search for oxides with small inversion energies; b) design of large inversion-energy oxide TIs that can be stabilized by pressure; and c) a search for covalent oxides where TI-removing atomic displacements can be effectively screened out.
机译:多年来一直在寻找稳定的氧化物拓扑绝缘体(TI),但没有发现。而较重的(硒化物,碲化物)硫属化物可以是TI。指出了拓扑绝热与热力学稳定性之间的基本矛盾,提供了一个狭窄的机会窗口。首先确定了电子基序,并可以在八面体位置将ABO(3)中的拓扑带反转为孤对,富电子的B原子(例如Te,I,Bi)。然后,在假定的钙钛矿结构中设计了十二种ABO3化合物,它们满足了该电子基序,并且通过密度函数理论计算的确是TI。接下来,说明了具有大反转能量的筛选不良的离子氧化物会经历降低能量的原子变形,这会破坏立方TI相的稳定性并消除能带反转。尽管如此,拓扑带反转和结构稳定性的共存窗口仍可以在中等压力下(BaTeO3和RbIO3分别为15和35 GPa)扩展。这项研究追踪了在环境压力下设计稳定的氧化物拓扑绝缘体所需的原理:a)寻找具有小反转能量的氧化物; b)设计可以通过压力稳定的大的转化能氧化物TI。 c)寻找可以有效筛选出去除TI的原子位移的共价氧化物。

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