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arXiv 0709.1130cond-mat.supr-concond-mat.str-el
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La $_{2-x}$ Ba $_{x}$ CuO $_4$中电荷密度波的性质

Properties of charge density waves in La$_{2-x}$Ba$_{x}$CuO$_4$

Young-June Kim, G. D. Gu, T. Gog, D. Casa

摘要:

本文报道了$\rm La_{2-x}Ba_xCuO_4 (x \approx 1/8)$中电荷密度波(条纹)有序的X射线散射研究,其中超导$T_c$被大大抑制。在该样品中观察到对应于电荷条纹的静态有序的强超晶格反射。根据所测量的70多个独特的超晶格位置的强度,推断了最低温度下的结构调制。我们发现该样品中的电荷序可用一维电荷密度波来描述,在相邻的$\rm CuO_2$平面上分别具有(0.23,0,0.5)和(0,0.23,0.5)的无公度波矢.由于电荷密度波阶的结构调制是简单的正弦曲线,没有观察到更高的谐波。在结构转变温度以下,出现短程电荷密度波关联,在40 K附近发展为大尺度电荷有序,接近自旋密度波有序温度。然而,这种电荷排序未能成长为一个真正的长程序,其相关长度饱和在$\sim 230Å$,并略有下降低于约15 K,这可能是由于二维超导的开始。

英文摘要:

We report a comprehensive x-ray scattering study of charge density wave (stripe) ordering in $\rm La_{2-x}Ba_xCuO_4 (x \approx 1/8)$, for which the superconducting $T_c$ is greatly suppressed. Strong superlattice reflections corresponding to static ordering of charge stripes were observed in this sample. The structural modulation at the lowest temperature was deduced based on the intensity of over 70 unique superlattice positions surveyed. We found that the charge order in this sample is described with one-dimensional charge density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0, 0.23, 0.5) respectively on neighboring $\rm CuO_2$ planes. The structural modulation due to the charge density wave order is simply sinusoidal, and no higher harmonics were observed. Just below the structural transition temperature, short-range charge density wave correlation appears, which develops into a large scale charge ordering around 40 K, close to the spin density wave ordering temperature. However, this charge ordering fails to grow into a true long range order, and its correlation length saturates at $\sim 230Å$, and slightly decreases below about 15 K, which may be due to the onset of two-dimensional superconductivity.

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