Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 90: Quantum Impurities and Kondo Physics

TT 90.3: Talk

Thursday, March 12, 2026, 17:30–17:45, CHE/0091

Orbital-Selective Mott transition in a U(1) gauge model of the Kondo lattice: a Quantum Monte Carlo study — •Gaopei Pan and Fakher Assaad — University of Würzburg, 97074 Würzburg, Germany

We investigate a U(1) gauge theory formulation of the dimensional mismatch Kondo model describing a spin chain on a semi-metallic surface. Using sign-problem-free determinant quantum Monte Carlo simulations, we compute the single-particle spectra, optical conductivity, and dynamical spin structure factor of the composite fermions across a wide range of parameters.

Our results reveal a clear evolution from a Kondo-screened heavy-fermion regime to a Kondo-breakdown phase where the composite fermion spectral weight collapses. Most strikingly, the zero-frequency optical conductivity displays a sharp suppression at the breakdown point, accompanied by a redistribution of spectral weight, which cannot be explained by simple band-structure effects. Instead, the data support an interpretation in terms of an orbital-selective Mott transition, where the f-sector becomes localized while the conduction c electrons remain itinerant.

Together, these findings provide unbiased numerical evidence for a gauge-fluctuation-driven Kondo breakdown and demonstrate how composite-fermion and optical conductivity can diagnose orbital-selective Mott transition in strongly correlated metals.

Keywords: Quantum Monte Carlo; Kondo Physics; U(1) gauge field; orbital-selective Mott transition