The Generalized Green's function Cluster Expansion: A Python package for simulating polarons

TL;DR

This paper introduces a Python package implementing the Generalized Green's function Cluster Expansion method, enabling efficient simulation of polaron properties across various models and conditions, suitable for both quick and large-scale computations.

Contribution

The paper presents a new, efficient implementation of the GGCE method for simulating polarons, adaptable to multiple electron-phonon couplings and temperature regimes.

Findings

Efficient computations on laptops using NumPy and SciPy.

Parallel scalable calculations with PETSc.

Applicable to diverse electron-phonon models.

Abstract

We present an efficient implementation of the Generalized Green's function Cluster Expansion (GGCE), which is a new method for computing the ground-state properties and dynamics of polarons (single electrons coupled to lattice vibrations) in model electron-phonon systems. The GGCE works at arbitrary temperature and is well suited for a variety of electron-phonon couplings, including, but not limited to, site and bond Holstein and Peierls (Su-Schrieffer-Heeger) couplings, and couplings to multiple phonon modes with different energy scales and coupling strengths. Quick calculations can be performed efficiently on a laptop using solvers from NumPy and SciPy, or in parallel at scale using the PETSc sparse linear solver engine.