Role of structural instability in high-temperature superconductivity and its effect on isotope effect
Role of structural instability in high-temperature superconductivity and its effect on isotope effect
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结构不稳定性在高温超导中的作用及其对同位素效应的影响
DOI：
10.1080/00150199208015075
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发表时间：
1992
期刊：
影响因子：
0.8
通讯作者：
Z. Fisk
中科院分区：
文献类型：
--
作者：
A. Bussmann;A. Bishop;A. Migliori;Z. Fisk
摘要采用非简谐电子-声子相互作用模型分析了La_（2-x）Sr_xCuO_4的四方-正交结构相变。x-依赖性以及温度T-依赖性的软模式的计算和定量与实验数据。为了评估软模式的超导性能的重要性Eliashberg方程求解此特定模式。由此产生的电子-声子耦合Λ被发现是强烈的x和T依赖与周围的结构转变温度Ts的特征异常。计算得到的超导转变温度Tc与实验值接近，但低估了Tc。这种差异是由于忽略了高阶电子-声子相互作用。包含这些项会导致同位素效应α从BCS值0·5大幅降低到变化值0·1。
Abstract The tetragonal-orthorhombic structural phase transition of La2-x Sr x CuO4 is analyzed within an anharmonic electron-phonon interaction model. x-dependence as well as temperature T-dependence of the soft mode are calculated and in quantitative agreement with experimental data. To evaluate the importance of the soft mode for the superconducting properties Eliashberg equations are solved for this specific mode. The resulting electron-phonon coupling Λ is found to be strongly x and T dependent with characteristic anomalies around the structural transition temperature T s . The calculated x-dependent superconducting transition temperature T c follows closely the experimental values but underestimates T c . This discrepancy is attributed to the neglect of higher order electron-phonon interactions. Inclusion of these terms leads to a strong decrease of the isotope effect α from the BCS value of 0·5 to a varied value of 0·1.