Electron-Phonon (De)Coupling In 2d

Electron phonon coupling in (quasi)-two-dimensional structures within the first order theory is strongly constrained by symmetry, and the resulting deficiencies are manifested in a number of striking phenomena: electronic system dynamically decoupled from lattice, absence of totally symmetric phonons, Jahn-Teller theorem violation (with spontaneous symmetry breaking), insufficiency of the Kohn singularity conditions, nonlinear acoustic branches. Here presented analysis of layered structures enlightens that this phenomena are enforced in highly symmetric structures (including here superconducting CuO2 sheet, atomically thin hexagonal boron nitride, graphene. e.g.). General group theoretical results covering all possible quasi-two-dimensional crystal structures are illustrated on real materials, as well as on a few hypothetical compounds.