Anomalous orbital dynamics inLaSrMnO4observed by Raman spectroscopy

Abstract

We report inelastic light scattering experiments on the single-layered manganite $\mathrm{La}\mathrm{Sr}\mathrm{Mn}{\mathrm{O}}_{4}$. The distinct features observed are the appearance of numerous symmetry-forbidden phonon peaks, with a strong temperature dependence of their intensity and frequency, and a double-peak structure of the activated high-frequency in-plane modes. These observations are ascribed to the conspicuous dynamics of an admixed ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbital present in the background of the crystal field stabilized ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbitals. Our study suggests a significant competition between the kinetic energy gain due to the resulting orbital canting and the strong crystal field splitting.