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Study of electronic phase transitions in composite copper oxides by intercalation

复合铜氧化物插层电子相变研究

基本信息

批准号：
07455001
负责人：
KOIKE Yoji
金额：
$ 4.86万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

We have studied changes of the anisotropy (dimensionality), The carrier concentration and the superconducting transition temperature Tc through intercalation of halogen in the Bi-based high-Tc superconductors, in order to obtain some informations on the mechanism of high-Tc superconductivity. The results obtained are as follows.1.We have found that the experimental results are explained by the multilayr model, where a high-Tc superconductor is regarded as an alternating stack of the CuO_2 layr (superconducting layr) and the so-called block layr (normal layr), taking account of the redistribution of carriers and of the proximity effect. Although the mechanism of the intrinsic superconductivity in the superconducting layrs remains unsettles, the attractive potential between electrons is estimated as ca. 2000 K.This means that the attractive potential is expected to be no longer caused by the phonon-mediated machanism but by another machanism due to a rather high-energy driving force.2.From the experiment of iodine intercaltion into the Co-substituted Bi2122 phase, we have found that the decrease in Tc through the iodine intercalation is attributed to not only the increase of the hole concentration in the CuO_2 planes but also the decoupling between adjacent blocks of the CuO_2 planes. This result supports the above-mentioned multilayr model.3.We have succeeded in making the Bi2222 phase superconducting through halogen intercalation. We have concluded that the role of the annealing under high pressures of oxygen in the appearance of superconductivity for the Bi2222 phase is to suppply the CuO_2 planes with enough hole carriers.

我们研究了卤素在铋基高Tc超导体中嵌入对各向异性（维数）、载流子浓度和超导转变温度Tc的变化，以期获得有关高Tc超导机理的一些信息。得到的结果如下：1。我们发现实验结果可以用多层模型来解释，在多层模型中，考虑到载流子的重新分布和邻近效应，高tc超导体被认为是CuO_2层（超导层）和所谓的块层（正常层）的交替堆叠。虽然超导层中本征超导的机制仍不确定，但估计电子间的吸引势约为2000 K。这意味着吸引势预计不再是由声子介导的机制引起的，而是由另一种机制引起的，这种机制是由一个相当高能的驱动力引起的。从碘插入共取代Bi2122相的实验中，我们发现碘插入后Tc的降低不仅是由于CuO_2面空穴浓度的增加，而且是由于CuO_2面相邻块之间的解耦。该结果支持上述多层模型。我们成功地通过卤素嵌入使Bi2222相超导。我们得出结论，高压氧退火在Bi2222相超导现象中的作用是为CuO_2平面提供足够的空穴载流子。