The GW space-time method for the self-energy of large systems

TL;DR

The paper introduces a GW space-time method that enhances computational efficiency and scalability for calculating the electronic structure of large systems using the GW approximation.

Contribution

It develops a real-space and imaginary-time representation of Green's function and screened Coulomb interaction, enabling study of larger systems than previously possible.

Findings

Efficient computation of self-energy using GW in real-space and imaginary-time.

Application to silicon demonstrates scalability to larger unit cells.

Improved computational performance over traditional methods.

Abstract

We present a detailed account of the GW space-time method. The method increases the size of systems whose electronic structure can be studied with a computational implementation of Hedin's GW approximation. At the heart of the method is a representation of the Green's function G and the screened Coulomb interaction W in the real-space and imaginary-time domain, which allows a more efficient computation of the self-energy approximation Sigma = iGW. For intermediate steps we freely change between representations in real and reciprocal space on the one hand, and imaginary time and imaginary energy on the other, using fast Fourier transforms. The power of the method is demonstrated using the example of Si with artificially increased unit cell sizes.