An unusual isotope effect in a high-transition-temperature superconductor
An unusual isotope effect in a high-transition-temperature superconductor
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DOI：
10.1038/nature02731
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发表时间：
2004-07-08
期刊：
影响因子：
64.8
通讯作者：
Lanzara, A
中科院分区：
文献类型：
--
作者：
Gweon, GH;Sasagawa, T;Lanzara, A
在传统的超导体中，允许超导性的电子配对是由虚声子的交换引起的，虚声子是晶格振动的量子。对于高转变温度（high-T-c）超导体来说，声子是否参与到配对中还远不清楚。例如，最佳掺杂的Bi2Sr2CaCu2O8+ δ （Bi2212；参考文献1）在氧同位素取代（O-16—> O-18导致T-c从92 K降至91 K）后，T-c的变化可以忽略不计，这通常被认为意味着声子在该材料中起着微不足道的作用。在这里，我们提供了包含不同氧同位素的Bi2212样品的电子动力学的详细比较，使用角分辨光发射光谱。我们的数据显示了明确而强烈的同位素效应。令人惊讶的是，这种效应主要出现在广泛的高能峰中，通常被称为“非相干峰”。作为温度和电子动量的函数，同位素效应的大小与超导间隙（即对结合能）密切相关。我们认为这些结果可以用动态自旋-佩尔斯图(2)来解释，其中电子的单线态配对和电子-晶格耦合相互增强。
In conventional superconductors, the electron pairing that allows superconductivity is caused by exchange of virtual phonons, which are quanta of lattice vibration. For high-transition-temperature (high-T-c) superconductors, it is far from clear that phonons are involved in the pairing at all. For example, the negligible change in T-c of optimally doped Bi2Sr2CaCu2O8+delta (Bi2212; ref. 1) upon oxygen isotope substitution (O-16 --> O-18 leads to T-c decreasing from 92 to 91 K) has often been taken to mean that phonons play an insignificant role in this material. Here we provide a detailed comparison of the electron dynamics of Bi2212 samples containing different oxygen isotopes, using angle-resolved photoemission spectroscopy. Our data show definite and strong isotope effects. Surprisingly, the effects mainly appear in broad high-energy humps, commonly referred to as 'incoherent peaks'. As a function of temperature and electron momentum, the magnitude of the isotope effect closely correlates with the superconducting gap-that is, the pair binding energy. We suggest that these results can be explained in a dynamic spin-Peierls picture(2), where the singlet pairing of electrons and the electron-lattice coupling mutually enhance each other.