arXiv 1201.28932012-01cond-mat.mtrl-sci

反转对称破缺的铁电PbTiO $_{3}$ / SrRuO $_{3}$超晶格

Ferroelectric PbTiO$_{3}$/SrRuO$_{3}$ superlattices with broken inversion symmetry

S. J. Callori, J. Gabel, D. Su, J. Sinsheimer, M. V. Fernandez-Serra, M. Dawber

备注：: To be published in Physical Review Letters
DOI：: 10.1103/PhysRevLett.109.067601

摘要：

采用超薄SrRuO $_{3}$层制备了PbTiO $_{3}$ /SrRuO $_{3}$超晶格。由于超晶格的几何形状，样品在其电阻率中显示出大的各向异性，这可以通过改变PbTiO $_{3}$层的厚度来控制。因此，沿着铁电方向，SrRuO $_{3}$层可以充当介电元件，而不是金属元件。我们发现，通过减少PbTiO $_{3}$的浓度，由于成分反转对称性破缺的极化不对称性的影响越来越重要。这些结果是有意义的，因为它们代表了一类新的铁电超晶格，具有丰富而复杂的相图。通过扩展我们的材料组，我们能够引入新的行为，这些行为只有在其中一种材料不是钙钛矿钛酸盐时才会发生。在这里，组成反转对称性破缺双色超晶格，由于超晶格内的A和B位离子的组合变化，证明使用实验测量和第一性原理密度泛函理论的组合。

英文摘要：

We have fabricated PbTiO$_{3}$/SrRuO$_{3}$ superlattices with ultra-thin SrRuO$_{3}$ layers. Due to the superlattice geometry, the samples show a large anisotropy in their electrical resistivity, which can be controlled by changing the thickness of the PbTiO$_{3}$ layers. Therefore, along the ferroelectric direction, SrRuO$_{3}$ layers can act as dielectric, rather than metallic, elements. We show that, by reducing the concentration of PbTiO$_{3}$, an increasingly important effect of polarization asymmetry due to compositional inversion symmetry breaking occurs. The results are significant as they represent a new class of ferroelectric superlattices, with a rich and complex phase diagram. By expanding our set of materials we are able to introduce new behaviors that can only occur when one of the materials is not a perovskite titanate. Here, compositional inversion symmetry breaking in bi-color superlattices, due to the combined variation of A and B site ions within the superlattice, is demonstrated using a combination of experimental measurements and first principles density functional theory.

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