Nonequilibrium variational-cluster approach to real-time dynamics in the Fermi-Hubbard model

TL;DR

This paper introduces a nonequilibrium variational-cluster method to analyze real-time dynamics in the 1D Fermi-Hubbard model, focusing on double occupancy after rapid hopping changes, with improved numerical stability.

Contribution

It develops a stable, numerically efficient approach using a simple reference system within nonequilibrium self-energy functional theory for the Fermi-Hubbard model.

Findings

Effective method for real-time dynamics analysis

Stable numerical implementation using time derivatives

Application to double occupancy after hopping quenches

Abstract

The nonequilibrium variational-cluster approach is applied to study the real-time dynamics of the double occupancy in the one-dimensional Fermi-Hubbard model after different fast changes of hopping parameters. A simple reference system, consisting of isolated Hubbard dimers, is used to discuss different aspects of the numerical implementation of the approach in the general framework of nonequilibrium self-energy functional theory. Opposed to a direct solution of the Euler equation, its time derivative is found to serve as numerically tractable and stable conditional equation to fix the time-dependent variational parameters.