Electron-phonon (de)coupling in kagome lattice

Electron-phonon coupling matrix elements are analyzed for special kagome systems consisting solely of special orbits. Decomposition of the dynamical representation is used for symmetry-based classification of normal modes and is juxtaposed with the symmetry of electronic states corresponding to irreducible representations at special points of the Brillouin zone. A significant lack of coupling terms is detected; in other words, it is found that at special points of the Brillouin zone, in highly symmetrical systems, there exist electronic states that are completely decoupled from phonons. Moreover, some of these decoupled states can be degenerate (higher-dimensional). Finally, all possible special kagome systems with decoupled electronic states are determined and presented.