Evolution of the Kondo resonance feature and its relationship to spin-orbit coupling across the quantum critical point in Ce₂Rh_1-xCo_xSi₃

Abstract

We investigate the evolution of the electronic structure of Ce₂Rh_{1- x}Co_xSi₃ as a function of x employing high resolution photoemission spectroscopy. Co substitution at the Rh sites in antiferromagnetic Ce₂RhSi₃ leads to a transition to a Kondo system, Ce₂CoSi₃ via the Quantum Critical Point (QCP) at x=0.6. High resolution photoemission spectra reveal distinct signature of the Kondo resonance feature (KRF) and its spin-orbit split component (SOC) in the whole composition range indicating finite Kondo temperature scale at QCP. The intensity ratio of KRF and SOC exhibits gradual increase with the decrease in temperature in the strong hybridization limit. The scenario is reversed if the Kondo temperature becomes lower than the Neel temperature. The dominant temperature dependence of the spin-orbit coupled feature in this regime suggests the importance of spin-orbit interactions in the realization of spin-density wave quantum criticality.