Nonequilibrium charge-Kondo transport through negative-U molecules

TL;DR

This paper analytically investigates nonequilibrium charge transport in negative-U molecules exhibiting the charge-Kondo effect, establishing a mapping to positive-U models to derive current-voltage characteristics and noise behavior.

Contribution

It introduces an exact mapping between negative-U and positive-U Anderson models, enabling analytical insights into nonequilibrium charge-Kondo transport phenomena.

Findings

Derived analytical expressions for nonlinear current-voltage characteristics.

Demonstrated the relation between charge-Kondo and spin-Kondo regimes.

Explained super-Poissonian noise at high temperatures in positive-U models.

Abstract

Low-temperature transport through molecules with effectively negative charging energy U exhibits a charge-Kondo effect. We explore this regime analytically by establishing an exact mapping between the negative-U and the positive-U Anderson models, which is suitable for the description of nonequilibrium transport. We employ this mapping to demonstrate the intimate relation between nonequilibrium tranport in the spin-Kondo and charge-Kondo regimes, and derive analytical expressions for the nonlinear current-voltage chracteristics as well as the shot noise in the latter regime. Applying the mapping in the opposite direction, we elucidate the finding of super-Poissonian noise in the positive-U Anderson model at high temperatures, by relating the correlations between spin flips to pair-tunneling processes at negative U.