Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Heavy Fermions

TT 17.14: Talk

Wednesday, March 28, 2007, 17:30–17:45, H18

Magnetic Phase Diagram of the Doped 2D Kondo Lattice Model: a DCA calculation — •Lee C. Martin and Fakher F. Assaad — Universität Würzburg, Germany

We apply an antiferromagnetic symmetry breaking implementation of the dynamical cluster approximation (DCA) to the two-dimensional hole-doped Kondo lattice model with hopping t and coupling J.

Precise calculations of single particle spectral functions compare well with exact BSS results at the particle-hole symmetric point. However, our DCA version, combined with a QMC cluster solver, also allows simulations away from particle-hole symmetry and has enabled us to map out the magnetic phase diagram of the model as a function of doping, coupling J/t and band structure.

At half-filling, our results show that the linear behaviour of the quasi-particle gap at small values of J/t is a direct consequence of particle-hole symmetry, which leads to nesting of the Fermi surface. Breaking the symmetry, by inclusion of a diagonal hopping term, results in a greatly reduced gap which appears to follow a Kondo scale.

Upon doping the magnetic phase observed at half-filling survives and ultimately gives way to a paramagnetic phase. Across this magnetic order disorder transition, we track the topology of the Fermi surface.