Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 19: Metall-Isolatorüberg
änge

TT 19.5: Vortrag

Donnerstag, 30. März 2000, 10:45–11:00, H18

Metal-insulator transition in a depleted Kondo lattice model. — •Fakher F. Assaad — Institut für Theoretische Physik III, Universität Stuttgart,Pfaffenwaldring 57, D-70550 Stuttgart

We consider a two-dimensional half-filled Kondo lattice model with exchange J and hopping t in which three out of four localized spins are removed in a regular way. Since this depletion maintains particle-hole symmetry, zero temperature quantum Monte Carlo simulations may be carried out on large (up to 500 spins) lattices (1). It is shown that the competition between the RKKY interaction and Kondo effect generates a metal-insulator transition. The origin of the metallic state is clear in the limit of large J/t where each localized spin captures a conduction electron in a singlet bound state. The remaining conduction electrons form the metal. At small values of J/t the RKKY interaction leads to ordering of the localized spins. Due to the nesting properties of the conduction electron Fermi surface, this ordering generates an insulating state.

(1) F.F. Assaad, Phys. Rev. Lett 83 796 (1999).