Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Kondo Physics, f-Electron Systems and Heavy Fermions

TT 6.1: Vortrag

Montag, 5. September 2022, 15:00–15:15, H22

Zooming in on heavy fermions in Kondo lattice models — Bimla Danu¹, Zihong Liu¹, Fakher Assaad¹, and •Marcin Raczkowski² — ¹Institut für Theoretische Physik und Astrophysik and Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, 97074 Würzburg, Germany — ²Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany

Resolving the heavy fermion band in the conduction electron momentum resolved spectral function of the Kondo lattice model (KLM) is challenging since, in the weak coupling limit, its spectral weight is exponentially small. To alleviate this limitation we consider a composite fermion operator, consisting of a conduction electron dressed by spin fluctuations that shares the same quantum numbers as the electron. Using auxiliary field quantum Monte Carlo simulations we show that for the SU(2) spin-symmetric model on the square lattice at half filling, the quasiparticle residue of the composite fermion tracks the Kondo coupling J_k. This result holds down to J_k/W = 0.05, with W the bandwidth, and confirms that magnetic ordering, present below J_k/W = 0.18, does not destroy the heavy quasiparticle. We also study the spectral function of the composite fermion in the ground state and at finite temperatures, for SU(N) generalizations of the KLM, as well as for ferromagnetic Kondo couplings, and compare our results to analytical calculations in the limit of high temperatures, large-N, large-S and large J_k.