Kondo destruction and valence fluctuations in an Anderson model

TL;DR

This paper investigates Kondo destruction and valence fluctuations at a quantum critical point in a mixed-valent Anderson model, revealing critical behavior in spin and charge responses relevant to heavy-fermion systems.

Contribution

It demonstrates Kondo destruction at a mixed-valent quantum critical point within an Anderson model with a pseudogapped density of states, highlighting critical charge and spin fluctuations.

Findings

Kondo energy scale collapses at the critical point

Charge-fluctuation spectrum becomes singular

Spin and charge responses scale with /T and H/T

Abstract

Unconventional quantum criticality in heavy-fermion systems has been extensively analyzed in terms of a critical destruction of the Kondo effect. Motivated by a recent demonstration of quantum criticality in a mixed-valent heavy-fermion system, \beta-YbAlB4, we study a particle-hole-asymmetric Anderson impurity model with a pseudogapped density of states. We demonstrate Kondo destruction at a mixed-valent quantum critical point, where a collapsing Kondo energy scale is accompanied by a singular charge-fluctuation spectrum. Both spin and charge responses scale with energy over temperature (\omega/T) and magnetic field over temperature (H/T). Implications for unconventional quantum criticality in mixed-valence heavy fermions are discussed.