Seminars & Lectures
|* TITLE||Multipoint correlation functions: spectral representation and numerical evaluation|
|* DATE / TIME||2021-03-29, 16:00|
| Four-point correlation functions on the real-frequency axis describe experimentally relevant properties, such as nonlocal susceptibilities, transport, and inelastic photon scattering, of the systems of interacting quantum particles. However, the non-perturbative computation of real-frequency multipoint functions has been intractable. In this talk, I will summarize our recently developed method for non-perturbatively computing multipoint functions and its applications [1, 2]. We have derived generalized spectral representations for multipoint functions that apply in all of the commonly used many-body frameworks : the imaginary-frequency Matsubara and the real-frequency zero-temperature and Keldysh formalisms. We have developed a numerical renormalization group (NRG) method for evaluating the spectral representations for local multipoint functions, which can treat temperatures and frequencies---imaginary or real---of all magnitudes, from large to arbitrarily small ones . I will present the numerical results of four-point vertex functions and resonant inelastic x-ray scattering (RIXS) spectra of quantum impurity systems.
 F. B. Kugler*, S.-S. B. Lee*, and J. von Delft, arXiv:2101.00707.
*: These authors contributed equally to this work.
 S.-S. B. Lee, F. B. Kugler, and J. von Delft, arXiv:2101.00708.
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