Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 9: Poster Session: Correlated Electrons
TT 9.30: Poster
Tuesday, September 28, 2021, 13:30–16:00, P
Four-point functions on the real-frequency axis – A spectral representation and its numerical evaluation — •Fabian B. Kugler1,2, Seung-Sup B. Lee2, and Jan von Delft2 — 1Rutgers University, USA — 2LMU Munich, Germany
We present spectral representations for multipoint correlation functions for each of three widely-used formalisms: the imaginary-frequency Matsubara formalism and the real-frequency zero-temperature as well as Keldysh formalisms. The spectral representations separate information on the system’s dynamics, encoded in universal partial spectral functions, from the correlators’ analytical properties, encoded in formalism-dependent convolution kernels [1]. We present numerical results for the four-point vertex of the Anderson impurity model, obtained by a novel numerical renormalization group scheme [2]. In the imaginary-frequency Matsubara formalism, our approach allows us to compute the vertex at arbitrarily low temperatures and to follow the complete crossover from strongly interacting particles to weakly interacting quasiparticles. In the real-frequency Keldysh formalism, we first benchmark our method against analytical results at weak and infinitely strong interaction. Then, we consider the dynamical mean-field solution of the Hubbard model to reveal the rich real-frequency structure of the vertex in the metal-insulator coexistence regime.
[1] F. B. Kugler, S.-S. B. Lee, J. von Delft, arXiv:2101.00707, accepted in PRX
[2] S.-S. B. Lee, F. B. Kugler, J. von Delft, arXiv:2101.00708, accepted in PRX