Probing the spin polarization of an Anderson impurity

TL;DR

This study uses spin-polarized scanning tunneling microscopy to investigate the spin polarization and Kondo effect of an Anderson impurity in MoS$_{2}$, providing experimental evidence and theoretical validation of impurity spin behavior under magnetic fields.

Contribution

It demonstrates the first direct measurement of spin polarization in an Anderson impurity within MoS$_{2}$ and validates theoretical models of the Kondo effect through quantitative analysis.

Findings

Magnetic field induces changes in impurity state peaks and Kondo resonance.

Spin-resolved spectral function shows notable polarization under magnetic field.

Impurity magnetization exhibits universality consistent with the $S=1/2$ Kondo effect.

Abstract

We report spin-polarized scanning tunneling microscopy measurements of an Anderson impurity system in MoS$_{2}$ mirror twin boundaries, where both the quantum confined impurity state and the Kondo resonance resulting from the interaction with the substrate are accessible. Using a spin-polarized tip, we observe magnetic field induced changes in the peak heights of the Anderson impurity states as well as in the magnetic field-split Kondo resonance. Quantitative comparison with numerical renormalization group calculations provides evidence of the notable spin polarization of the spin-resolved impurity spectral function under the influence of a magnetic field. Moreover, we extract the field and temperature dependence of the impurity magnetization from the differential conductance measurements and demonstrate that this exhibits the universality and asymptotic freedom of the $S=1/2$ Kondo effect. This work shows that mirror twin boundaries can be used as a testing ground for theoretical predictions on quantum impurity models.