Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 34: Correlated Electrons: Spin Systems and Itinerant Magnets

TT 34.1: Vortrag

Freitag, 31. März 2006, 10:15–10:30, HSZ 301

Nonmagnetic Impurities in the Two-Dimensional Kondo-Necklace — •Wolfram Brenig — Institute for Theoretical Physics, Technical University of Braunschweig, Germany

The effects of nonmagnetic impurities on the two-dimensional spin-1/2 Kondo-necklace model are investigated. In its undoped state this spin-model displays a quantum-critical point at a Kondo-exchange coupling of J≈ 1.4 which separates a dimerized singlet-phase from an antiferromagnetically ordered ground state. Using quantum Monte-Carlo calculations based on the stochastic series expansion, results will be presented for the uniform susceptibility and the staggered structure factor as a function of temperature, impurity concentration, and Kondo exchange. It will be shown, that on dilution of the Kondo sites the systems develops quasi-free moments with a renormalized Curie-constant. Moreover, the quantum critical point is suppressed, with a disorder induced long-range antiferromagnetic order to appear also in the singlet phase, which amounts to an order-from-disorder phenomenon.