Coulomb blockade and Non-Fermi-liquid behavior in quantum dots

TL;DR

This paper explores the non-Fermi-liquid behavior in quantum dots, revealing a line of two-channel Kondo fixed points and transitions between Fermi-liquid regimes influenced by tunneling asymmetry and Coulomb interactions.

Contribution

It demonstrates the existence of a continuous transition from spin to charge two-channel Kondo effects and shows the crossover temperature can be significantly increased, making the phenomena experimentally accessible.

Findings

Identification of a line of two-channel Kondo fixed points.

Transition between Fermi-liquid regimes with different conductance.

Enhanced crossover temperature for the two-channel Kondo effect.

Abstract

The non-Fermi-liquid properties of an ultrasmall quantum dot coupled to a lead and to a quantum box are investigated. Tuning the ratio of the tunneling amplitudes to the lead and box, we find a line of two-channel Kondo fixed points for arbitrary Coulomb repulsion on the dot, governing the transition between two distinct Fermi-liquid regimes. The Fermi liquids are characterized by different values of the conductance. For an asymmetric dot, spin and charge degrees of freedom are entangled: a continuous transition from a spin to a charge two-channel Kondo effect evolves. The crossover temperature to the two-channel Kondo effect is greatly enhanced away from the local-moment regime, making this exotic effect accessible in realistic quantum-dot devices.