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arXiv:2507.20385 · Physical review. B./Physical review. B

Third-order strong-coupling impurity solver for real-frequency dynamical mean field theory: Accurate spectral functions for antiferromagnetic and photodoped states

Lei Geng, Aaram J. Kim, Philipp Werner

Published Nov 8, 2025• 3 citations
arXivHTMLPDF

Abstract

Strong-coupling expansions for impurity models up to third order are implemented here on the real-time axis using a quantics tensor cross interpolation framework. This approach provides an accurate impurity solver that can describe both equilibrium systems and nonequilibrium steady states in the intermediate to strong-interaction regime.
DOI
10.1103/jjjl-v1pj

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We introduce a neural network impurity solver for real-frequency DMFT that employs a multihead cross-attention mechanism to map hybridization functions to spectral functions, conditioned on impurity parameters. Trained on high-quality MPS data from complex contour time evolution and incorporating derivative constraints with respect to the complex-time angle, our model achieves smooth generalization to the real-frequency axis. Benchmarking on the single-band Hubbard model for the Bethe lattice demonstrates quantitative accuracy across metallic, strongly correlated, and insulating regimes.