Comment on "Scaling feature of magnetic field induced Kondo-peak splittings"

TL;DR

This paper critiques a recent study on Kondo resonance splitting under magnetic fields, arguing that their findings were due to parameter choices and clarifying the true crossover behavior occurs at higher fields.

Contribution

It demonstrates that the previously observed anomalies are caused by parameter choices and clarifies the actual crossover point in Kondo resonance splitting.

Findings

Incorrect parameter choices led to misinterpretation of results.

The crossover occurs at magnetic fields comparable to the charge scale.

Reproduces the splitting behavior with correct parameters.

Abstract

In a recent work Zhang and coworkers (PRB 82, 075111 (2010)) studied the Zeeman splitting of the Kondo resonance for the single impurity Anderson model in a finite magnetic field $B$ with the numerical renormalization group (NRG) method. There, it was found that with increasing magnetic field $B$ the position of the Kondo resonance in the total spectral function \textit{does not} approach its position in the spin resolved spectral function. Additionally, the position of the Kondo maximum exceeded the Zeeman energy for $B/ T_K\gtrsim 5-10$, where $T_K$ is the low energy Kondo scale of the model ($g=2$, $\mu_B=k_B=\hbar=1$). In this comment we argue that both these findings are produced by an improper choice of NRG parameter values. However, we reproduce the crossover in the splitting from Kondo-like behavior to a non-universal splitting larger than the Zeeman energy, but this crossover occurs at much larger fields of the order of the charge scale.