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Quantum Dynamics Made Fast: Achieving Linear Time-Scaling for Nonequilibrium Green Functions

ORAL

Abstract

The accurate description of the nonequilibrium dynamics in correlated quantum-many-body systems remains to be a driving force for current research in condensed-matter physics and beyond.
Among others, the nonequilibrium Green functions (NEGF) method has proven to be a powerful tool to reliably predict the quantum dynamics, without being limited to 1D or spatially homogeneous systems. However, NEGF simulations are computationally expensive due to their T3 scaling with the simulation duration T. With the introduction of the generalized Kadanoff–Baym ansatz[1] (GKBA) T2 scaling could be achieved for second-order Born (SOA) selfenergies[2], which has substantially extended the scope of NEGF simulations. Recently[3], we could show that GKBA-NEGF simulations can be performed with order T1 scaling for SOA, GW, and T-matrix selfenergies, and even for the screened-ladder approximation[4]. Here, we show numerical results for various many-body approximations and demonstrate that a tremendous computational speed-up can be achieved in practice.

[1] P. Lipavský et al., Phys. Rev. B 34, 6933 (1986)
[2] S. Hermanns et al., Phys. Scr. 2012 014036 (2012)
[3] N. Schlünzen et al.,Phys. Rev. Lett. 124, 076601 (2020)
[4] J.-P. Joost et al., Phys. Rev. B 101, 245101 (2020)

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Presenters

  • Niclas Schlünzen

    ITAP, University of Kiel, University of Kiel, Institute of Theoretical Physics and Astrophysics, Kiel University, Germany, Univ Kiel, CAU Kiel, Germany

Authors

  • Niclas Schlünzen

    ITAP, University of Kiel, University of Kiel, Institute of Theoretical Physics and Astrophysics, Kiel University, Germany, Univ Kiel, CAU Kiel, Germany

  • Jan-Philip Joost

    ITAP, University of Kiel, University of Kiel, Institute of Theoretical Physics and Astrophysics, Kiel University, Germany, Univ Kiel, CAU Kiel, Germany

  • Michael Bonitz

    Kiel University, ITAP, University of Kiel, University of Kiel, Institute of Theoretical Physics and Astrophysics, Kiel University, Germany, Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Univ Kiel, CAU Kiel, Germany