Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 13: Correlated Electrons: Method Development I
TT 13.11: Talk
Monday, March 9, 2026, 17:45–18:00, HSZ/0101
Finite-difference parquet method and the strong-coupling pseudogap — Jae-Mo Lihm1,2, Dominik Kiese3, Seung-Sup B. Lee2, and •Fabian B. Kugler4,3 — 1Université Catholique de Louvain, Louvain-la-Neuve, Belgium — 2Seoul National University, Seoul, Korea — 3Flatiron Institute, New York, USA — 4University of Cologne, Cologne, Germany
We present the finite-difference parquet method [1], a two-particle diagrammatic approach with nonperturbative input. It takes the fully irreducible two-particle vertex from a reference solution while requiring only its full vertex explicitly. Using dynamical mean-field theory (DMFT) as a reference, this yields a reformulation of the parquet dynamical vertex approximation circumventing ill-behaved two-particle irreducible vertices. We use this method to investigate the pseudogap phase of the underdoped Hubard model. Our numerical results are consistent with diagrammatic Monte Carlo simulations and shed new light on the microscopic mechanism of the strong-coupling pseudogap: With dominant short-ranged antiferromagnetic spin fluctuations, we find an enhanced electron-paramagnon scattering amplitude crucial for the pseudogap opening. The form of this enhancement, reflected in the real part of the Hedin vertex, requires strong local correlations from DMFT as well as nonlocal correlations in multiple two-particle channels from solving the parquet equations.
[1] https://arxiv.org/abs/2505.20116
Keywords: Parquet formalism; Dynamical vertex approximation; Dynamical mean-field theory; Hubbard model; Pseudogap