Dynamic Evanescent Phonon Coupling Across the La1-xSrxMnO3/SrTiO3 Interface

The transport and magnetic properties of correlated La0.53Sr0.47MnO3 ultrathin films, grown epitaxially on SrTiO3, show a sharp cusp at the structural transition temperature of the substrate. Using a combination of experiment and first principles theory we show that the cusp is a result of evanescent cross-interface coupling between the charge carriers in the film and a soft phonon mode in the SrTiO3, mediated through linked oxygen octahedral motions. The amplitude of the mode diverges at the transition temperature, and phonons are launched into the first few atomic layers of the film, affecting its electronic state.