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arXiv 0911.0970cond-mat.supr-concond-mat.mtrl-scicond-mat.str-el
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超导体Sr2-xBaxCuO3 +y的面外效应

Out of plane effect on the superconductivity of Sr2-xBaxCuO3+y with Tc up to 98K

W. B. Gao, Q. Q. Liu, L. X. Yang, Y. Yu, F. Y. Li, C. Q. Jin, S. Uchida

摘要:

采用高压高温合成法制备了一系列新的Sr_(2-x)CuO_(3 +y)(0x0.6)超导体。的Rietveld细化的基础上,粉末X射线衍射证实,超导体结晶在K2 NiF 4型结构的空间群I4/mmm类似的La 2CuO 4,但部分占据顶端的氧网站。结果表明,Ba取代Sr_2CuO_(3 +y)超导体的超导转变温度T_c随载流子掺杂量的增加而增大,常数d不仅受顶端O原子的有序/无序控制,而且受Ba含量控制。当x=0.6时,材料的Tc_(max)达到98 K,达到了单层铜氧化物超导体中Tc的最高值,高于具有最佳顶氧原子的Sr_2CuO_3 +y的Tc_(max)= 95 K。Sr_(2-x)CuO_(3 +y)中存在Sr位无序,这可能导致Tc的降低。结果表明,另一种效应超过了无序效应,这与面内Cu-O键长的增加或由于具有较大阳离子尺寸的Ba取代而延长的顶-O距离有关。本实验表明,Cu-O平面外的局部几何结构的优化可以显着提高铜氧化物超导体的Tc。

英文摘要:

A series of new Sr2-xBaxCuO3+y (0 x 0.6) superconductors were prepared using high-pressure and high-temperature synthesis. A Rietveld refinement based on powder x-ray diffraction confirms that the superconductors crystallize in the K2NiF4-type structure of a space group I4/mmm similar to that of La2CuO4 but with partially occupied apical oxygen sites. It is found that the superconducting transition temperature Tc of this Ba substituted Sr2CuO3+y superconductor with constant carrier doping level, i.e., constant d, is controlled not only by order/disorder of apical-O atoms but also by Ba content. Tcmax =98 K is achieved in the material with x=0.6 that reaches the record value of Tc among the single-layer copper oxide superconductors, and is higher than Tc=95K of Sr2CuO3+y with optimally ordered apical-O atoms. There is Sr-site disorder in Sr2-xBaxCuO3+y which might lead to a reduction of Tc. The result indicates that another effect surpasses the disorder effect that is related either to the increased in-plane Cu-O bond length or to elongated apical-O distance due to Ba substitution with larger cation size. The present experiment demonstrates that the optimization of local geometry out of the Cu-O plane can dramatically enhance Tc in the cuprate superconductors.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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