Local quantum criticality in an SU(4) spin-orbital coupled Kondo system

In this talk, I will discuss a theory of quantum criticality in a spin-orbital coupled Kondo system [1]. Electronic localization-delocalization has played a prominent role in realizing beyond-Landau metallic quantum critical points [2-4]. It typically involves local spins induced by strong correlations, with a “small” to “large” jump of the Fermi surface being one of its characteristic features. The involvement of multipolar degrees of freedom opens up a new window into --and novel platforms for the exploration of—unconventional metallic quantum criticality [5].

 

Here, we report analytical results regarding the fate of an SU(4) spin-orbital Kondo state in a multipolar Bose-Fermi Kondo model, which provides an effective description of a multipolar Kondo lattice [1,5]. We show that a generic trajectory in the parameter space contains two quantum critical points, which are associated with the destruction of the Kondo entanglement in the orbital and spin channels respectively. Our asymptotically exact results reveal a global phase diagram, provide the theoretical basis for the notion of sequential Kondo destruction, and lead to the theoretical understanding of the surprising experimental observation of TWO STAGES of Fermi-surface jumps in a multipolar heavy fermion compound Ce3Pd20Si6 [5]. Our findings point to new forms of quantum criticality that may still be realized in a variety of strongly correlated metals.