Multi-parameter scaling of the Kondo effect in quantum dots with an even number of electrons

TL;DR

This paper investigates how the Kondo temperature in quantum dots with an even number of electrons varies with the energy difference between singlet and triplet states, revealing a parameter-dependent crossover in scaling behavior.

Contribution

It demonstrates that the Kondo scaling involves multiple parameters, leading to model-dependent results and a crossover from universal to nonuniversal power-law behavior.

Findings

Kondo temperature decreases with increasing singlet-triplet energy difference

Crossover from universal to nonuniversal power-law scaling occurs

Scaling behavior depends on microscopic model parameters

Abstract

We address a recent theoretical discrepancy concerning the Kondo effect in quantum dots with an even number of electrons where spin-singlet and -triplet states are nearly degenerate. We show that the discrepancy arises from the fact that the Kondo scaling involves many parameters, which makes the results depend on concrete microscopic models. We illustrate this by the scaling calculations of the Kondo temperature, $T_K$, as a function of the energy difference between the singlet and triplet states $\Delta$. $T_K(\Delta)$ decreases with increasing $\Delta$, showing a crossover from a power law with a universal exponent to that with a nonuniversal exponent. The crossover depends on the initial parameters of the model.