Kondo screening in Co adatoms with full Coulomb interaction

Angelo Valli,Michael Karolak,Marc Philipp Bahlke,Giorgio Sangiovanni,Alexander Kowalski,Carmen Herrmann

doi:10.1103/physrevresearch.2.033432

Angelo Valli, Michael Karolak + Show 4 more

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https://doi.org/10.1103/physrevresearch.2.033432

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Abstract

Using a numerically exact first-principles many-body approach, we revisit the "prototypical" Kondo case of a cobalt impurity on copper. Even though this is considered a well understood example of the Kondo effect, we reveal an unexpectedly strong dependence of the screening properties on the parametrization of the local Coulomb tensor. As a consequence, the Kondo temperature can vary by orders of magnitude depending on the complexity of the parametrization of the electron-electron interaction. Further, we challenge the established picture of a spin-$1$ moment involving two cobalt $d$-orbitals only, as orbital-mixing interaction terms boost the contribution of the remainder of the $d$-shell.

Highlights

The Kondo effect arises when a local magnetic moment is quantum mechanically screened by the conduction electrons of a metallic host
In order to investigate the screening of the impurity magnetic moment we sample the spin-spin response function in imaginary time within CT-quantum Monte Carlo (QMC): χi j (τ ) = g2 Siz(τ )Szj (0), (7)
As the moment is screened by the conduction electrons, the spin susceptibility has a crossover to a Pauli behavior due to the onset of a Fermi liquid (FL) regime: χ −1(T ) ∝ T +TFL, with the characteristic coherence temperature TFL corresponding to TK in the case of a single impurity [40,41]

Summary

Introduction

The Kondo effect arises when a local magnetic moment is quantum mechanically screened by the conduction electrons of a metallic host. As a direct consequence of the screening of the impurity magnetic moment, the spin susceptibility undergoes a crossover from a Curie-Weiss to a Pauli behavior upon lowering the temperature. The Abrikosov-Suhl-Kondo resonance [2,3,4] emerges in the electronic spectral function at the Fermi level. Magnetic response functions and electron transport are suitable probes of the Kondo effect. The Fermiliquid properties emerging below the Kondo temperature TK are typically reached via smooth crossovers rather than with sharp transitions, complicating the experimental detection

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Conclusion