Achieving the Ultimate Scaling Limit for Nonequilibrium Green Functions Simulations

TL;DR

This paper introduces a new computational method that significantly reduces the complexity of nonequilibrium Green functions simulations, enabling more efficient analysis of strongly correlated fermionic systems in higher dimensions.

Contribution

A novel approach to GKBA-NEGF simulations that achieves linear scaling with simulation duration, greatly enhancing computational efficiency.

Findings

Achieved T-linear scaling in NEGF simulations.

Demonstrated enhanced simulation capabilities for complex quantum systems.

Extended the applicability of NEGF methods to larger and more complex problems.

Abstract

The dynamics of strongly correlated fermions following an external excitation reveals extremely rich collective quantum effects. Examples are fermionic atoms in optical lattices, electrons in correlated materials, and dense quantum plasmas. Presently, the only quantum-dynamics approach that rigorously describes these processes in two and three dimensions is nonequilibrium Green functions (NEGF). However, NEGF simulations are computationally expensive due to their $T^3$ scaling with the simulation duration $T$. Recently, $T^2$ scaling was achieved with the generalized Kadanoff--Baym ansatz (GKBA) which has substantially extended the scope of NEGF simulations. Here we present a novel approach to GKBA-NEGF simulations that is of order $T$, and demonstrate its remarkable capabilities.