The pseudogap Fermi-Bose Kondo model

TL;DR

This paper studies a magnetic impurity model with both fermionic and bosonic excitations, revealing how spin fluctuations suppress the Kondo effect and identifying critical behavior relevant to high-temperature superconductors and heavy-fermion systems.

Contribution

It introduces a combined Fermi-Bose Kondo model analyzed via renormalization group and large-N methods, highlighting the impact of spin fluctuations on Kondo physics and critical exponents.

Findings

Kondo temperature is significantly reduced by spin fluctuations.

Derived an exact critical exponent for the conduction electron T matrix.

Connections made to experimental observations in cuprate superconductors and heavy-fermion metals.

Abstract

We consider a magnetic impurity coupled to both fermionic quasiparticles with a pseudogap density of states and bosonic spin fluctuations. Using renormalization group and large-N calculations we investigate the phase diagram of the resulting Fermi-Bose Kondo model. We show that the Kondo temperature is strongly reduced by low-energy spin fluctuations, and make connections to experiments in cuprate superconductors. Furthermore we derive an exact exponent for the critical behavior of the conduction electron T matrix, and propose our findings to be relevant for certain scenarios of local quantum criticality in heavy-fermion metals.