Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany.
Nat Mater. 2012 Jul 15;11(8):675-81. doi: 10.1038/nmat3378.
The electron-phonon interaction is of central importance for the electrical and thermal properties of solids, and its influence on superconductivity, colossal magnetoresistance and other many-body phenomena in correlated-electron materials is the subject of intense research at present. However, the non-local nature of the interactions between valence electrons and lattice ions, often compounded by a plethora of vibrational modes, presents formidable challenges for attempts to experimentally control and theoretically describe the physical properties of complex materials. Here we report a Raman scattering study of the lattice dynamics in superlattices of the high-temperature superconductor YBa(2)Cu(3)O(7) (YBCO) and the colossal-magnetoresistance compound La(2/3)Ca(1/3)MnO(3) that suggests a new approach to this problem. We find that a rotational mode of the MnO(6) octahedra in La(2/3)Ca(1/3)MnO(3) experiences pronounced superconductivity-induced line-shape anomalies, which scale linearly with the thickness of the YBCO layers over a remarkably long range of several tens of nanometres. The transfer of the electron-phonon coupling between superlattice layers can be understood as a consequence of long-range Coulomb forces in conjunction with an orbital reconstruction at the interface. The superlattice geometry thus provides new opportunities for controlled modification of the electron-phonon interaction in complex materials.
电子-声子相互作用对于固体的电学和热学性质至关重要，其对超导性、庞磁电阻和其他关联电子材料中的多体现象的影响是当前研究的热点。然而，价电子和晶格离子之间相互作用的非局域性质，通常还伴随着大量的振动模式，这给试图从实验上控制和理论上描述复杂材料的物理性质带来了巨大的挑战。在这里，我们报告了对高温超导材料 YBa(2)Cu(3)O(7) (YBCO) 和庞磁电阻化合物 La(2/3)Ca(1/3)MnO(3) 的超晶格中晶格动力学的喇曼散射研究，该研究提出了一种解决该问题的新方法。我们发现，La(2/3)Ca(1/3)MnO(3)中 MnO(6) 八面体的一个旋转模式表现出明显的超导诱导线形状异常，其线宽随 YBCO 层的厚度线性变化，范围长达数十纳米。超晶格层之间的电子-声子耦合的传递可以理解为长程库仑力与界面处的轨道重构的共同作用的结果。因此，超晶格几何结构为在复杂材料中控制电子-声子相互作用的修饰提供了新的机会。
