Long-range transfer of electron-phonon coupling in oxide superlattices

Abstract

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 currently the subject of intense research. However, the non-local nature of the interactions between valence electrons and lattice ions, often compounded by a plethora of vibrational modes, present 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 $\mathbf{YB}{\mathbf{a}}_2\mathbf{C}{\mathbf{u}}_3{\mathbf{O}}_7$ and the colossal-magnetoresistance compound $\mathbf{L}{\mathbf{a}}_{2/3}\mathbf{C}{\mathbf{a}}_{1/3}\mathbf{Mn}{\mathbf{O}}_3$ that suggests a new approach to this problem. We find that a rotational mode of the MnO${}_6$ octahedra in $\mathbf{L}{\mathbf{a}}_{2/3}\mathbf{C}{\mathbf{a}}_{1/3}\mathbf{Mn}{\mathbf{O}}_3$ experiences pronounced superconductivity-induced lineshape anomalies, which scale linearly with the thickness of the $\mathbf{YB}{\mathbf{a}}_2\mathbf{C}{\mathbf{u}}_3{\mathbf{O}}_7$ layers over a remarkably long range of several tens of nanometers. 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.

13 pages, 4 figures. Revised version to be published in Nature Materials