Performance of wave function and Green's function methods for non-equilibrium many-body dynamics

Theoretical descriptions of the non-equilibrium dynamics of quantum many-body systems essentially employ either (i) explicit treatments, relying on the truncation of the expansion of the many-body wave function, (ii) compressed representations of the many-body wave function, or (iii) evolution of an...

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Main Authors: Cian C. Reeves, Gaurav Harsha, Avijit Shee, Yuanran Zhu, Thomas Blommel, Chao Yang, K. Birgitta Whaley, Dominika Zgid, Vojtěch Vlček
Format: Article
Language:English
Published: American Physical Society 2025-04-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.7.023002
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author Cian C. Reeves
Gaurav Harsha
Avijit Shee
Yuanran Zhu
Thomas Blommel
Chao Yang
K. Birgitta Whaley
Dominika Zgid
Vojtěch Vlček
author_facet Cian C. Reeves
Gaurav Harsha
Avijit Shee
Yuanran Zhu
Thomas Blommel
Chao Yang
K. Birgitta Whaley
Dominika Zgid
Vojtěch Vlček
author_sort Cian C. Reeves
collection DOAJ
description Theoretical descriptions of the non-equilibrium dynamics of quantum many-body systems essentially employ either (i) explicit treatments, relying on the truncation of the expansion of the many-body wave function, (ii) compressed representations of the many-body wave function, or (iii) evolution of an effective (downfolded) representation through Green's functions. In this work, we select representative cases of each of the methods and address how these complementary approaches capture the dynamics driven by intense field perturbations to non-equilibrium states. Under strong driving, the systems are characterized by strong entanglement of the single-particle density matrix and natural populations approaching those of a strongly interacting equilibrium system. We generate a representative set of results that are numerically exact and form a basis for a critical comparison of the distinct families of methods. We demonstrate that the compressed formulation based on similarity-transformed Hamiltonians (coupled-cluster approach) is practically exact in weak fields and, hence, weakly or moderately correlated systems. Coupled cluster, however, struggles for strong driving fields, under which the system exhibits strongly correlated behavior, as measured by the von Neumann entropy of the single-particle density matrix. The dynamics predicted by Green's functions in the (widely popular) GW approximation are less accurate, but improve significantly upon the mean-field results in the strongly driven regime.
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spelling doaj-art-064bde9f07ce4f7ea0f08bcd6d7584012025-08-20T01:54:58ZengAmerican Physical SocietyPhysical Review Research2643-15642025-04-017202300210.1103/PhysRevResearch.7.023002Performance of wave function and Green's function methods for non-equilibrium many-body dynamicsCian C. ReevesGaurav HarshaAvijit SheeYuanran ZhuThomas BlommelChao YangK. Birgitta WhaleyDominika ZgidVojtěch VlčekTheoretical descriptions of the non-equilibrium dynamics of quantum many-body systems essentially employ either (i) explicit treatments, relying on the truncation of the expansion of the many-body wave function, (ii) compressed representations of the many-body wave function, or (iii) evolution of an effective (downfolded) representation through Green's functions. In this work, we select representative cases of each of the methods and address how these complementary approaches capture the dynamics driven by intense field perturbations to non-equilibrium states. Under strong driving, the systems are characterized by strong entanglement of the single-particle density matrix and natural populations approaching those of a strongly interacting equilibrium system. We generate a representative set of results that are numerically exact and form a basis for a critical comparison of the distinct families of methods. We demonstrate that the compressed formulation based on similarity-transformed Hamiltonians (coupled-cluster approach) is practically exact in weak fields and, hence, weakly or moderately correlated systems. Coupled cluster, however, struggles for strong driving fields, under which the system exhibits strongly correlated behavior, as measured by the von Neumann entropy of the single-particle density matrix. The dynamics predicted by Green's functions in the (widely popular) GW approximation are less accurate, but improve significantly upon the mean-field results in the strongly driven regime.http://doi.org/10.1103/PhysRevResearch.7.023002
spellingShingle Cian C. Reeves
Gaurav Harsha
Avijit Shee
Yuanran Zhu
Thomas Blommel
Chao Yang
K. Birgitta Whaley
Dominika Zgid
Vojtěch Vlček
Performance of wave function and Green's function methods for non-equilibrium many-body dynamics
Physical Review Research
title Performance of wave function and Green's function methods for non-equilibrium many-body dynamics
title_full Performance of wave function and Green's function methods for non-equilibrium many-body dynamics
title_fullStr Performance of wave function and Green's function methods for non-equilibrium many-body dynamics
title_full_unstemmed Performance of wave function and Green's function methods for non-equilibrium many-body dynamics
title_short Performance of wave function and Green's function methods for non-equilibrium many-body dynamics
title_sort performance of wave function and green s function methods for non equilibrium many body dynamics
url http://doi.org/10.1103/PhysRevResearch.7.023002
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