Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 16: Correlated Electrons: Method Development
TT 16.11: Talk
Wednesday, September 7, 2022, 12:30–12:45, H10
Connecting real- and imaginary-frequency axis for two-particle many-body propagators — •Selina Dirnböck1, Sebastian Huber1, Seung-Sup Lee2,3, Fabian Kugler4, Jan von Delft3, Karsten Held1, and Markus Wallerberger1 — 1TU Wien, Austria — 2Seoul National University, South Korea — 3Ludwig-Maximilians-Universität München, Germany — 4Rutgers University, New Jersey, USA
Two-particle response functions are a centerpiece of quantum many-body physics, relating both to experiment, where they can be observed as susceptibilities, and to theory, where they form the basis of advanced self-consistent field theories. Yet, due to their size and complex structure, they are challenging to handle numerically.
Recently, two advances have been made to tackle this problem: firstly, the intermediate representation together with an overcomplete basis (IR+OB), which provides a highly efficient compression of propagators in imaginary frequency, and secondly, partial spectral functions (PSFs), which allow for the efficient evaluation in real frequency, by, for example, using the numerical renormalization group (NRG).
In this talk, we connect these two approaches: we show that the IR+OB and PSFs are intimately connected. We also show that the two-particle propagator obtained from NRG/PSFs on the real-frequency axis can be compressed efficiently using IR+OB on imaginary-frequency axis, reducing the memory demand by more than three orders of magnitude. Finally, we use the guidance from PSFs to develop a physical regularization scheme for the IR+OB.