Dynamical and anharmonic effects on the electron-phonon coupling and the zero-point renormalization of the electronic structure

TL;DR

This study investigates how dynamical and anharmonic effects influence electron-phonon interactions and zero-point renormalization of electronic structures in various crystals, revealing significant corrections beyond traditional approximations.

Contribution

The paper introduces a dynamical scheme for frequency-dependent self-energy calculations and explores anharmonic effects using a non-perturbative approach, advancing understanding of electron-phonon coupling.

Findings

Satellite bands below Fermi level in LiF and MgO

Zero-point renormalization reduced by up to 40% when including dynamical effects

High-order electron-phonon coupling significantly impacts ZPR in some materials

Abstract

The renormalization of the band structure at zero temperature due to electron-phonon coupling is investigated in diamond, BN, LiF and MgO crystals. We implement a dynamical scheme to compute the frequency-dependent self-energy and the resulting quasiparticle electronic structure. Our calculations reveal the presence of a satellite band below the Fermi level of LiF and MgO. We show that the renormalization factor (Z), which is neglected in the adiabatic approximation, can reduce the zero-point renormalization (ZPR) by as much as 40%. Anharmonic effects in the renormalized eigenvalues at finite atomic displacements are explored with the frozen-phonon method. We use a non-perturbative expression for the ZPR, going beyond the Allen-Heine-Cardona theory. Our results indicate that high-order electron-phonon coupling terms contribute significantly to the zero-point renormalization for certain materials.