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

TL;DR

This paper investigates how electron-phonon interactions influence the electronic properties of a two-dimensional electron gas with strong spin-orbit coupling, revealing effective strong coupling effects due to topological Fermi surface changes.

Contribution

It provides a numerical analysis of electron self-energy and spectral properties in a 2D Rashba system with phonons, highlighting the impact of spin-orbit coupling on electron-phonon interactions.

Findings

Strong spin-orbit coupling enhances electron-phonon effects.

Fermi surface topology change causes a divergence in the density of states.

Even weak interactions can lead to effective strong coupling in certain regimes.

Abstract

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 non-crossing 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.