The Bose-Fermi Kondo model with a singular dissipative spectrum: Exact solutions and their implications

TL;DR

This paper presents an exact solution to the sub-ohmic Bose-Fermi Kondo model with a singular bosonic spectrum, revealing dominant longitudinal fluctuations and implications for local quantum criticality with zero residual entropy.

Contribution

It provides the first exact solution for the singular Bose-Fermi Kondo model, elucidating the nature of critical fluctuations and their impact on quantum critical heavy fermion systems.

Findings

Singular bosonic spectrum leads to exact solvability.

Longitudinal fluctuations dominate over transverse ones.

Results support zero residual entropy in local quantum critical solutions.

Abstract

Quantum dissipation induces a critical destruction of a Kondo screened state, which is of interest in the contexts of quantum critical heavy fermion metals and magnetic nanostructures. The sub-ohmic Bose-Fermi Kondo model provides a setting to study this effect. We find that this many-body problem is exactly solvable when the spectrum of the dissipative bosonic bath, J(\omega), is singular, corresponding to J(\tau)=const.. We determine the local spin correlation functions, showing that the singular LONGITUDINAL fluctuations of the bosonic bath dominate over the transverse ones. Our results provide evidence that the local quantum critical solution, derived within the extended dynamical mean field approach to the Kondo lattice model, has a zero residual entropy.