Adiabatic Preparation of a Correlated Symmetry-Broken Initial State with the Generalized Kadanoff--Baym Ansatz

TL;DR

This paper demonstrates that using the generalized Kadanoff--Baym Ansatz (GKBA), one can efficiently prepare a correlated symmetry-broken initial state, such as an excitonic insulator, through an adiabatic switching process, with practical switching times.

Contribution

It introduces a method to adiabatically prepare a correlated symmetry-broken state within GKBA, validated against imaginary-time Dyson equation solutions.

Findings

Successful adiabatic switching to a symmetry-broken state

Feasibility within reasonably short switching times

Validation against imaginary-time Dyson equation

Abstract

A fast time propagation method for nonequilibrium Green's functions based on the generalized Kadanoff--Baym Ansatz (GKBA) is applied to a lattice system with a symmetry-broken equilibrium phase, namely an excitonic insulator. The adiabatic preparation of a correlated symmetry-broken initial state from a Hartree--Fock wave function within GKBA is assessed by comparing with a solution of the imaginary-time Dyson equation. We find that it is possible to reach a symmetry-broken correlated initial state with nonzero excitonic order parameter by the adiabatic switching procedure. We discuss under which circumstances this is possible in practice within reasonably short switching times.