Photo-emission signatures of coherence breakdown in Kondo alloys: dynamical mean-field theory approach

Abstract

We study the Kondo alloy model on a square lattice using dynamical meanfield theory (DMFT) for Kondo substitution and disorder effects, together with static meanfield approximations. We computed and analyzed photoemission properties as a function of electronic filling n c , Kondo impurity concentration x, and strength of Kondo temperature T K . We provide a complete description of the Angle Resolved Photoemission Spectroscopy (ARPES) signals expected in the paramagnetic Kondo phases. By analyzing the Fermi surface, we observe the Lifshitz-like transition predicted previously for strong T K at x = n c and we discuss the evolution of the dispersion from the dense coherent to the dilute Kondo regimes. At smaller T K , we find that this transition marking the breakdown of coherence at x = n c becomes a crossover. However, we identify another transition at a smaller concentration x where the effective mass continuously vanishes. x separates the one-branch and the twobranches ARPES dispersions characterizing respectively dilute and dense Kondo paramagnetic regimes. The x − T K phase diagrams are also described, suggesting that the transition at x might be experimentally observable since magnetically ordered phases are stabilized at much lower T K . Fermi surface reconstructions in antiferromagnetic and ferromagnetic phases are also discussed.