Zero-Temperature Magnetic Transition in an Easy-Axis Kondo Lattice Model --- An NRG Study

Antiferromagnetic heavy fermion metals close to their quantum critical points display a richness in their physical properties unanticipated by the traditional approach to quantum criticality. Here we address the quantum transition of a spin-$\frac{1}{2}$ antiferromagnetic Kondo lattice model with an easy-axis anisotropy within the extended dynamical mean field theory. We derive results [1] in real frequency using the bosonic numerical renormalization group (bNRG) method and compare them with Quantum Monte Carlo results in Matsubara frequency. The bNRG results show a logarithmic divergence in the critical local spin susceptibility, signaling a destruction of Kondo screening. The $T=0$ transition is nearly second order, with any jump in the magnetic order parameter {\em not} exceeding a few percents of the full moment. The bNRG results also display some subtle features; we discuss their possible origins and suggest means for further microscopic studies. [1] J.-X. Zhu, S. Kirchner, R. Bulla, and Q. Si, cond-mat/0607567.