通过极化畸变避免SrTiO3（001）上的LaAlO3覆盖层中的极化突变
Avoiding the polarization catastrophe in LaAlO3 overlayers on SrTiO3(001) through a polar distortion
摘要：
一个明显的均匀的极性畸变延伸到几个单位电池，使薄的LaAlO3覆盖层SrTiO 3（001），以抵消电荷偶极子，从而中和“极化灾难”，这是建议由简单的离子计数。从密度泛函理论计算得到的这种未预料到的机制允许LaAlO3覆盖层的几个晶胞保持绝缘（因此，完全离子化）。该系统的带隙，定义由占用O $2p$状态在表面和未占用的Ti 3d状态在界面处，在某些情况下$\sim$ 20 μ m的距离，随着厚度的增加的LaAlO3膜之前的绝缘体到金属的过渡和交叉到电子重建发生在大约5个单层的LaAlO3。
英文摘要：
A pronounced uniform polar distortion extending over several unit cells enables thin LaAlO3 overlayers on SrTiO3(001) to counteract the charge dipole and thereby neutralize the "polarization catastrophe" that is suggested by simple ion-counting. This unanticipated mechanism, obtained from density functional theory calculations, allows several unit cells of the LaAlO3 overlayer to remain insulating (hence, fully ionic). The band gap of the system, defined by occupied O $2p$ states at the surface and unoccupied Ti 3d states at the interface in some cases $\sim$20 Ådistant, decreases with increasing thickness of the LaAlO3-film before an insulator-to-metal transition and a crossover to an electronic reconstruction occurs at around five monolayers of LaAlO3.
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