Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 90: Quantum Impurities and Kondo Physics
TT 90.2: Talk
Thursday, March 12, 2026, 17:15–17:30, CHE/0091
Kondo impurities coupled to a Chern insulator — •David A. Krüger1 and Michael Potthoff1,2 — 1Department of Physics, University of Hamburg, Hamburg, Germany — 2The Hamburg Centre for Ultrafast Imaging, Hamburg, Germany
We study a system consisting of two spin-1/2 impurities that are exchange-coupled to a two-dimensional Qi-Wu-Zhang Chern insulator. The interplay between the truncated Kondo effect, the truncated RKKY interaction, and the mass parameter m gives rise to a complex phase diagram comprising RKKY singlet and triplet phases, the Kondo singlet, and a partially Kondo-screened phase. Furthermore, we examine how the phase diagram depends on the coupling orbitals and the inter-impurity distance.
Using a Lanczos transformation, we map the problem to a one-dimensional chain with the impurities at the first site, which is then solved using an adaptive natural-orbital configuration-interaction technique. We also consider fictitious local magnetic fields Zeeman-coupled to the impurity spins. The field directions form a four-dimensional base manifold M ≅ S2 × S2. The bundle of ground states over M can be topologically characterized by a Chern number that differs from the usual k-space Chern number and provides further insight into the limit of classical impurity spins.
Keywords: gapped Kondo-impurity model; Chern Insulator