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TT: Fachverband Tiefe Temperaturen

TT 48: Poster Session: Many Body Systems, Quantum Critical Phenomena

TT 48.12: Poster

Mittwoch, 18. März 2020, 15:00–19:00, P2/4OG

Fast Nonequilibrium Green Functions simulations with GW selfenergies — •Christopher Makait, Niclas Schlünzen, Jan-Philip Joost, and Michael Bonitz — Institut für Theoretische Physik und Astrophysik, CAU Kiel, Germany

The Nonequilibrium Green Functions (NEGF)[1] method is a powerful tool to compute time-dependent expectation values of single-particle observables in correlated quantum many-body systems. Its unfavorable N_t³-scaling with propagation time N_t could be reduced to N_t² by introduction of the Generalized Kadanoff–Baym Ansatz (GKBA)[2]. Recently, an exact time-local (N_t¹) reformulation of the GKBA, the G1–G2 scheme [3,4], has been found for various self energies, which makes this method viable for long time simulations.
In a general basis the G1–G2 scheme has a computationally expensive scaling with basis size (N_b⁵–N_b⁶). For the uniform electron gas (UEG) however, we found an advantageous N_b³N_t¹ scaling for both second-order and GW selfenergies, which makes this scheme particularly interesting for this system. Here, we present first results of the application of the G1–G2 scheme to the UEG.

[1] L. P. Kadanoff, G. Baym, Quantum Statistical Mechanics (Benjamin, New York, 1962)

[2] P. Lipavský, V. Špička, B. Velický, Phys. Rev. B34, 6933 (1986)

[3] N. Schlünzen, Jan-Philip Joost, Michael Bonitz, submitted, arXiv:1909.11489 [cond-mat.str-el]

[4] M. Bonitz, Quantum Kinetic Theory (Springer, 2016)