Multiple magnetic impurities on surfaces: Scattering and quasiparticle interference

TL;DR

This paper investigates the complex behavior of multiple magnetic impurities on metallic surfaces, focusing on their interactions, the transition to independent impurity behavior, and the resulting quasiparticle interference patterns.

Contribution

It introduces a detailed analysis of impurity interactions and the conditions for independent impurity behavior using numerical renormalization group calculations.

Findings

Identification of the minimum impurity separation for independent impurity description.

Definition of a 'dilute cluster' limit for higher impurity densities.

Calculation of quasiparticle interference patterns for multiple impurities.

Abstract

We study systems of multiple interacting quantum impurities deposited on a metallic surface in a 3D host. For the real-space two-impurity problem, using numerical renormalization group calculations, a rich range of behavior is shown to arise due to the interplay between Kondo physics and effective RKKY interactions - provided the impurity separation is small. Such calculations allow identification of the minimum impurity separation required for a description in terms of independent impurities, and thereby the onset of the 'dilute impurity limit' in many-impurity systems. A 'dilute cluster' limit is also identified in systems with higher impurity density, where inter-impurity interactions are only important within independent clusters. We calculate the quasiparticle interference (QPI) due to two and many impurities, and explore the consequences of the independent impurity/cluster paradigms. Our results provide a framework to investigate the effects of disorder due to interacting impurities at experimentally relevant surface coverages.