Kondo destruction quantum critical point from the magnetic side: Bose-Fermi Kondo model in a large S expansion

The quantum critical phenomena associated with the destruction of the Kondo effect in heavy fermion systems lie beyond the Ginzburg-Landau framework [1-4]. The Bose-Fermi Kondo model provides an effective model for the Kondo destruction quantum criticality, displaying such unconventional physics as the Planckian dynamical scaling and non-Fermi liquid behavior. A persistent challenge of the subject is the challenge to study the Kondo destruction quantum phase transition from the magnetic side. Here we overcome this challenge in the model by analyzing it in the large-S limit (where S is the spin size in the SU(2) symmetric model) [5]. We do so using a momentum-shell renormalization-group approach. We identify the fixed points that control the continuous transition between a local-moment phase and a Kondo-screened heavy Fermi liquid, thereby establishing a controlled framework for Kondo-destruction quantum criticality from the magnetic side.