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TT: Fachverband Tiefe Temperaturen
TT 109: Frustrated Magnets - (General) Theory
TT 109.5: Talk
Friday, March 16, 2018, 10:30–10:45, H 3005
Frustrated quantum magnetism in the Kondo-lattice on the zig-zag ladder — •Matthias Peschke, Roman Rausch, and Michael Potthoff — I. Institut für Theoretische Physik, Universität Hamburg
The interplay between Kondo effect, indirect magnetic interaction and geometrical frustration is studied in the Kondo lattice on the one-dimensional zig-zag ladder. Using the density-matrix renormalization group (DMRG), the ground state and various short- and long-range spin- and density-correlation functions are calculated for the model at half-filling as a function of the antiferromagnetic Kondo interaction down to J=0.3t where t is the nearest-neighbor hopping.
Geometrical frustration is shown to lead to at least two critical points: Starting from the strong-J limit, where almost local Kondo screening dominates, antiferromagnetic correlations between nearest-neighbor and next-nearest-neighbor local spins become stronger and stronger, until at Jcdim ≈ 0.895 frustration is alleviated by a spontaneous breaking of translational symmetry and a corresponding transition to a dimerized state. Furthermore, within the symmetry-broken dimerized state, our data suggest a magnetic transition to a 90∘ quantum spin spiral with quasi-long-range order at Jcmag ≈ 0.84. The quantum-critical point is characterized by a diverging spin-structure factor S(q) at wave vector q=π/2 and the closure of the spin gap (based on system sizes up to L=40). This is opposed to the model on the one-dimensional bipartite chain, which is known to have a finite spin gap for all J>0 at half-filling.