Do quantum dots allow one access to pseudogap Kondo physics?

TL;DR

This paper investigates whether quantum dots can access pseudogap Kondo physics, analyzing how a suppressed density of states at the Fermi level influences Kondo behavior and screening in such systems.

Contribution

The study explores the effects of a power-law suppressed density of states on Kondo physics in quantum dots, extending understanding of pseudogap Kondo models to experimental quantum dot setups.

Findings

Pseudogap Kondo physics can manifest in quantum dots with power-law suppressed density of states.

Incomplete screening of local moments occurs at low temperatures in these systems.

The behavior depends on particle-hole symmetry and the power-law exponent r.

Abstract

For the last decade, tunable quantum dot systems have allowed the investigation of Kondo physics wherein the quenching of a single spin on an artificial atom affects the conductance. The pseudogap Kondo model featuring a density of states $\rho(\epsilon)$ = C$|\epsilon|^{r}$, introduced by Withoff and Fradkin in 1990 was predicted to exhibit Kondo-like physics above a critical value of the Kondo coupling, J$_c$, which several groups have shown by numerical renormalization group (RG) is finite for r$< {1/2}$. Gonzalez-Buxton {\it{et al}} showed that the strong coupling limit of the particle-hole symmetric model leads to a non-trivial $\frac{\pi (1-r)}{2}$ phase shift at low temperatures indicating incomplete screening of the local moment, while away from particle-hole symmetry one generically flows towards a ground state with $\delta \sim \pi$. We examine the implications of this model for quantum dots whose leads are Fermi-liquid-like, yet possess a tunneling density of states which is suppressed at the Fermi energy as a power law.