Electron-phonon coupling reflecting dynamic charge inhomogeneity in copper oxide superconductors
Electron-phonon coupling reflecting dynamic charge inhomogeneity in copper oxide superconductors
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DOI：
10.1038/nature04704
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发表时间：
2006-04-27
期刊：
影响因子：
64.8
通讯作者：
Tranquada, JM
中科院分区：
文献类型：
--
作者：
Reznik, D;Pintschovius, L;Tranquada, JM
由于这些系统中存在多种强相互作用，理解铜氧化物超导体的尝试变得复杂。许多人认为反铁磁性对于超导性很重要，但人们对电子晶格耦合的可能作用重新产生了兴趣(1-4)。传统超导体MgB2具有非常强的电子-晶格耦合，涉及标准理论预测并通过实验定量证实的特定振动模式（声子）（5）。在这里，我们提出的非弹性散射测量结果表明，氧化铜超导体 La2-xSrxCuO4（x=0.07、0.15）中的 Cu-O 键拉伸声子存在类似的强烈异常。传统理论无法预测这种行为。 La1.875Ba0.125CuO4 和 La1.48Nd0.4Sr0.12CuO4 的异常现象最强，这些化合物表现出空间调制的电荷和磁序，通常称为条带序 (6)；它发生在与电荷顺序相对应的波矢量处。这些结果表明，这种巨大的电子声子异常在未掺杂和过度掺杂的非超导体中不存在，与电荷不均匀性有关。由此可见，电子声子耦合对于我们理解超导性可能很重要，尽管它的贡献可能是间接的。
The attempt to understand copper oxide superconductors is complicated by the presence of multiple strong interactions in these systems. Many believe that antiferromagnetism is important for superconductivity, but there has been renewed interest in the possible role of electron-lattice coupling(1-4). The conventional superconductor MgB2 has a very strong electron-lattice coupling, involving a particular vibrational mode (phonon) that was predicted by standard theory and confirmed quantitatively by experiment(5). Here we present inelastic scattering measurements that show a similarly strong anomaly in the Cu-O bond-stretching phonon in the copper oxide superconductors La2-xSrxCuO4 (with x=0.07, 0.15). Conventional theory does not predict such behaviour. The anomaly is strongest in La1.875Ba0.125CuO4 and La1.48Nd0.4Sr0.12CuO4, compounds that exhibit spatially modulated charge and magnetic order, often called stripe order(6); it occurs at a wave vector corresponding to the charge order. These results suggest that this giant electron-phonon anomaly, which is absent in undoped and over-doped non-superconductors, is associated with charge inhomogeneity. It follows that electron-phonon coupling may be important to our understanding of superconductivity, although its contribution is likely to be indirect.