Spin versus charge noise from Kondo traps

TL;DR

This paper investigates how Kondo correlations differently affect magnetic and charge noise in solid state devices, revealing that spin noise exhibits universal behavior linked to the Kondo temperature, unlike charge noise.

Contribution

It demonstrates through numerical renormalization group analysis that spin noise universally depends on the Kondo temperature, whereas charge noise remains describable by single-particle theory even in the Kondo regime.

Findings

Spin noise is a universal function of the Kondo temperature.

Charge noise remains well described by single-particle theory in the Kondo regime.

The difference persists despite disorder, affecting noise management strategies.

Abstract

Magnetic and charge noise have common microscopic origin in solid state devices, as described by a universal electron trap model. In spite of this common origin, magnetic (spin) and charge noise spectral densities display remarkably different behaviours when many-particle correlations are taken into account, leading to the emergence of the Kondo effect. Our numerical renormalization group results indicate that while spin noise is a universal function of the Kondo temperature, charge noise remains well described by single-particle theory even when the trap is deep in the Kondo regime. This difference survives even in the presence of disorder, showing that noise can be more manageable in devices that are sensitive to magnetic (rather than charge) fluctuations and that the signature of the Kondo effect can be observed in spin noise spectroscopy experiments.