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

TL;DR

This study reveals that electron-phonon interactions in oxide superlattices can be transferred over long distances, enabling new ways to control material properties like superconductivity and magnetoresistance through layered structures.

Contribution

It demonstrates long-range transfer of electron-phonon coupling in oxide superlattices, a novel approach for manipulating physical properties of complex materials.

Findings

Superconductivity-induced anomalies in Raman spectra scale with layer thickness.

Electron-phonon coupling transfer occurs over tens of nanometers.

Long-range Coulomb forces and orbital reconstruction facilitate this transfer.

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 $\bf YBa_2 Cu_3 O_7$ and the colossal-magnetoresistance compound $\bf La_{2/3}Ca_{1/3}MnO_{3}$ that suggests a new approach to this problem. We find that a rotational mode of the MnO$_6$ octahedra in $\bf La_{2/3}Ca_{1/3}MnO_{3}$ experiences pronounced superconductivity-induced lineshape anomalies, which scale linearly with the thickness of the $\bf YBa_2 Cu_3 O_7$ 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.