Max-Planck-Institute for Chemical Physics of Solids, Physics of Correlated Matter, Nöthnitzer Street 40, D-01187 Dresden, Germany.
Nat Commun. 2013;4:2449. doi: 10.1038/ncomms3449.
An hour-glass-shaped magnetic excitation spectrum appears to be a universal characteristic of the high-temperature superconducting cuprates. Fluctuating charge stripes or alternative band structure approaches are able to explain the origin of these spectra. Recently, an hour-glass spectrum has been observed in an insulating cobaltate, thus favouring the charge stripe scenario. Here we show that neither charge stripes nor band structure effects are responsible for the hour-glass dispersion in a cobaltate within the checkerboard charge-ordered regime of La(2-x)Sr(x)CoO(4). The search for charge stripe ordering reflections yields no evidence for charge stripes in La(1.6)Sr(0.4)CoO(4), which is supported by our phonon studies. With the observation of an hour-glass-shaped excitation spectrum in this stripeless insulating cobaltate, we provide experimental evidence that the hour-glass spectrum is neither necessarily connected to charge stripes nor to band structure effects, but instead, probably intimately coupled to frustration and arising chiral or non-collinear magnetic correlations.
沙漏形磁激发谱似乎是高温超导铜酸盐的普遍特征。电荷条纹或交替能带结构的方法能够解释这些谱的起源。最近，在绝缘的钴酸盐中观察到了沙漏谱，因此支持电荷条纹的情景。在这里，我们表明，在 La(2-x)Sr(x)CoO(4)的棋盘状电荷有序相中，既不是电荷条纹，也不是能带结构效应导致钴酸盐中的沙漏色散。对电荷条纹有序反射的搜索没有为 La(1.6)Sr(0.4)CoO(4)中的电荷条纹提供证据，我们的声子研究也支持了这一点。在这个无条纹的绝缘钴酸盐中观察到沙漏形激发谱，我们提供了实验证据，表明沙漏谱既不一定与电荷条纹有关，也不一定与能带结构效应有关，而是可能与挫折以及出现的手性或非共线磁关联密切相关。
