Quantum criticality and the break-up of the Kondo pseudo-potential

TL;DR

This paper explores the role of charge degrees of freedom in heavy electron quantum criticality, proposing that the collapse of the Fermi surface involves a return of nominal to real valence, linked to the Kondo pseudo-potential.

Contribution

It introduces the concept that quantum criticality involves a local charge degree of freedom, connecting Anderson's valence ideas with the collapse of the Fermi surface in heavy fermion systems.

Findings

Identification of the Kondo pseudo-potential with a charged background.

Proposal that the Fermi surface collapse is a valence change.

Discussion of a large N Schwinger boson scheme for the mechanism.

Abstract

We discuss how Anderson's ideas of nominal and real valence can be incorporated into the current discussion of heavy electron quantum criticality. In the heavy electron phase, the nominal valence of a screened magnetic ion differs from its real valence by one unit. We identify this discrepancy with the formation of a positively charged background we call the Kondo pseudo-potential. At the quantum critical point, the sudden collapse of the heavy electron Fermi surface can be identified with the return of the nominal to the real valence. This leads to the interesting idea that the heavy electron quantum critical point may involve locally critical charge degrees of freedom. We discuss how this might come about within a large N Schwinger boson scheme.