Electron-phonon effects on spin-orbit split bands of two-dimensional systems

The electronic self-energy is studied for a two-dimensional electron gas coupled to a spin-orbit Rashba field and interacting with dispersionless phonons. For the case of a momentum independent electron-phonon coupling (Holstein model) we solve numerically the self-consistent noncrossing approximation for the self-energy and calculate the electron mass enhancement m(*)/m and the spectral properties. We find that, even for nominal weak electron-phonon interaction, for strong spin-orbit couplings the electrons behave as effectively strongly coupled to the phonons. We interpret this result by a topological change of the Fermi surface occurring at sufficiently strong spin-orbit coupling, which induces a square-root divergence in the electronic density of states at low energies. We provide results for m(*)/m and for the density of states of the interacting electrons for several values of the electron filling and of the spin-orbit interaction.