Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 79: Correlated Electrons - Poster Session

TT 79.23: Poster

Mittwoch, 2. April 2014, 15:00–19:00, P2

Magnetic phase-diagram of the spin-diluted Kondo-lattice model — •Matthias Peschke, Maximilian Aulbach, and Michael Potthoff — Universität Hamburg I. Institut für Theoretische Physik, Hamburg , Germany

We analyze the magnetic phase diagram of the spin-diluted Kondo-lattice model for strong antiferromagnetic Kondo couplings J and fillings ranging from quarter filling down to the magnetic-polaron limit with a single conduction electron. This range of electron densities permits to employ the Lanczos method for systems consisting of a moderate number of lattice sites and local spins. At quarter filling, and for a “diluted” system where every second site of the conduction-electron system couples to a local quantum spin s=1/2, the formation of almost local Kondo singlets results in a non-magnetic ground state. For low densities we expect a state with magnetic long-range order of the local spins mediated by extremely heavy polarons. In the single conduction-electron limit, an almost fully polarized ferromagnet is enforced by a generalized Lieb-Mattis theorem. While the size of the Kondo clouds is predominantly controlled by J, the polaron size is additionally determined by the degree of spin dilution. We study the crossover from polaron-mediated magnetism to a non-magnetic state with local spins screened individually for different degrees of dilution and for different J in the strong-coupling regime.