MESA+ Institute for Nanotechnology, University of Twente, Post Office Box 217, 7500AE Enschede, The Netherlands.
Phys Rev Lett. 2013 Aug 30;111(9):096102. doi: 10.1103/PhysRevLett.111.096102. Epub 2013 Aug 27.
A recent theoretical study [Phys. Rev. B 85, 121411(R) (2012)] predicted a thickness limit below which ideal polar cuprates turn nonpolar driven by the associated electrostatic instability. Here we demonstrate this possibility by inducing a structural transformation from the bulk planar to chainlike structure upon reducing the SrCuO2 repeat thickness in SrCuO2/SrTiO3 superlattices with unit-cell precision. Our results, based on structural investigation by x-ray diffraction and high resolution scanning transmission electron microscopy, demonstrate that the oxygen sublattice can essentially be built by design. In addition, the electronic structure of the chainlike structure, as studied by x-ray absorption spectroscopy, shows the signature for preferential hole occupation in the Cu 3d(3z2-r2) orbital, which is different from the planar case.
最近的一项理论研究[Phys. Rev. B 85, 121411(R) (2012)]预测，在相关静电不稳定性的驱动下，理想极性铜酸盐在厚度低于某一极限时将变为非极性。在这里，我们通过在 SrCuO2/SrTiO3 超晶格中以单胞精度减小 SrCuO2 的重复厚度，诱导从体平面到链状结构的结构转变，证明了这种可能性。我们的结果基于 x 射线衍射和高分辨率扫描透射电子显微镜的结构研究，表明氧亚晶格基本上可以通过设计构建。此外，通过 x 射线吸收光谱研究的链状结构的电子结构显示出 Cu 3d(3z2-r2)轨道中优先占据空穴的特征，这与平面情况不同。
