Critical theories for the pseudogap Kondo problem

TL;DR

This paper analyzes quantum phase transitions in the pseudogap Kondo problem using renormalization group techniques and perturbative expansions near critical dimensions, providing effective field theories for the critical points.

Contribution

It introduces effective low-energy field theories for the critical fixed points of the pseudogap Kondo problem using perturbative and renormalization group methods.

Findings

Effective field theories for critical fixed points

Perturbative expansions near r=0 and r=1

Insights into quantum phase transitions in pseudogap systems

Abstract

We discuss quantum phase transitions in the pseudogap Kondo problem, which describes a magnetic moment coupled to conduction electrons with a power-law density of states, rho(omega) ~ |omega|^r. We show that different perturbative expansions, together with renormalization group techniques, provide effective low-energy field theories for the relevant critical fixed points. In particular, we review expansions near the lower-critical and upper-critical dimensions of the problem, being r=0 and r=1, respectively.