Mixed Quantum-Classical Methods for Polaron Spectral Functions

TL;DR

This paper compares semiclassical methods for calculating polaron spectral functions, demonstrating their efficiency and accuracy in modeling electron-phonon interactions relevant for photoemission experiments.

Contribution

It introduces and evaluates the mean-field Ehrenfest and MASH approaches for spectral function calculations in polaron systems, highlighting their applicability to realistic models.

Findings

Both methods accurately reproduce spectral features across coupling regimes.

They are computationally efficient for ab initio polaron models.

The approaches reveal strengths and weaknesses depending on system parameters.

Abstract

In this work, using two distinct semiclassical approaches, namely the mean-field Ehrenfest (MFE) method and the mapping approach to surface hopping (MASH), we investigate the spectral function of a single charge interacting with phonons on a lattice. This quantity is relevant for the description of angle-resolved photoemission experiments. Focusing on the one-dimensional Holstein model, we compare the performance of these approaches across a range of coupling strengths and lattice sizes, exposing the relative strengths and weaknesses of each. We demonstrate that these approaches can be efficiently applied with reasonable accuracy to ab initio polaron models. Our work provides a route to the calculation of spectral properties in realistic electron-phonon-coupled systems in a computationally inexpensive manner with encouraging accuracy.