Condensed Matter Physics &Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA.
Sci Rep. 2016 Nov 22;6:37624. doi: 10.1038/srep37624.
The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here we provide direct observations of the evolution of the superstructure in LaCaMnO in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystal (ELC) phases. Moreover, our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations.
掺杂锰氧化物的基态电子有序通常与晶格调制有关，这有助于它们具有许多有趣的性质。然而，仅使用倒空间探针测量晶格超结构的热演化可能会导致具有竞争性解释的模糊结果。在这里，我们使用透射电子显微镜（TEM）技术提供了在实空间以及倒空间中观察 LaCaMnO 中超结构演变的直接证据。我们表明，这些转变是位错增殖和电子相分离的结果。由此产生的状态可以很好地用与电子液晶（ELC）相相关的对称性来描述。此外，我们的结果解决了关于非调谐超结构起源的长期争议，并提出了一个与最近理论计算一致的新结构模型。
