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首页> 外文期刊>RSC Advances >Two-dimensional polar metals in KNbO3/BaTiO3 superlattices: first-principle calculations
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Two-dimensional polar metals in KNbO3/BaTiO3 superlattices: first-principle calculations

机译：KNbO3 / BaTiO3超晶格中的二维极性金属：第一性原理计算

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Polar metals, commonly defined by the coexistence of polar structure and metallicity, are thought to be scarce because free carriers eliminate internal dipoles that may arise owing to asymmetric charge distributions. By using first-principle electronic structure calculations, we explored the possibility of producing metallic states in the polaronpolar KNbO _(3) /BaTiO _(3) superlattice (SL) composed of two prototypical ferroelectric materials: BaTiO _(3) (BTO) and KNbO _(3) (KNO). Two types of polaronpolar interfaces, p-type (KO) ~(?) /(TiO _(2) ) ~(0) and n-type (NbO _(2) ) ~(+) /(BaO) ~(0) , which can be constituted into two symmetric NbO _(2) /BaO–NbO _(2) /BaO (NN-type) and KO/TiO _(2) –KO/TiO _(2) (PP-type) SL, as well as one asymmetric KO/TiO _(2) –NbO _(2) /BaO (PN-type) SL. The spatial distribution of ferroelectric distortions and their conductive properties are found to be extraordinarily sensitive to the interfacial configurations. An insulator-to-metal transition is found in each unit cell of the symmetric interfacial SL models: one exhibiting quasi-two-dimensional n-type conductivity for NN-type SL, while the other being quasi-two-dimensional p-type conductivity for PP-type SL. The anisotropic coexistence of in-plane orientation of free carriers and out-of-plane orientation of ferroelectric polarization in KNO/BTO SL indicates that in-plane free carriers can not eliminate the out-of-plane dipoles. Our results provide a road map to create two-dimensional polar metals in insulating perovskite oxide SL, which is expected to promote applications of new quantum devices.
机译：通常由极性结构和金属性的共存定义的极性金属被认为是稀缺的，因为自由载流子消除了由于不对称电荷分布而可能产生的内部偶极子。通过使用第一性原理电子结构计算，我们探索了由两种典型铁电材料组成的极性/非极性KNbO _（3）/ BaTiO _（3）超晶格（SL）中产生金属态的可能性：BaTiO _（3）（ BTO）和KNbO _（3）（KNO）。两种极性/非极性界面，p型（KO）〜（？）/（TiO _（2））〜（0）和n型（NbO _（2））〜（+）/（BaO）〜 （0），可分为两个对称的NbO _（2）/ BaO–NbO _（2）/ BaO（NN型）和KO / TiO _（2）–KO / TiO _（2）（PP-型），以及一种不对称的KO / TiO _（2）–NbO _（2）/ BaO（PN型）SL。发现铁电畸变的空间分布及其导电特性对界面构型异常敏感。在对称界面SL模型的每个晶胞中发现了从绝缘体到金属的过渡：一个对NN型SL表现出准二维n型电导率，而另一个对准二维p型电导率表现出用于PP型SL。在KNO / BTO SL中，自由载流子的面内取向与铁电极化的面外取向的各向异性共存表明，面内自由载子不能消除面外偶极子。我们的结果提供了在绝缘钙钛矿氧化物SL中创建二维极性金属的路线图，有望促进新型量子器件的应用。

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