Measuring spin and charge correlations via tunneling-current conductance fluctuations

TL;DR

This paper demonstrates that tunneling-current conductance fluctuations in scanning tunneling microscopy can reveal detailed two-particle correlations, such as spin and charge susceptibilities, in interacting electron systems, exemplified by the Kondo effect.

Contribution

It introduces a theoretical framework linking conductance noise to two-particle correlations, enabling probing of collective excitations via standard tunneling experiments.

Findings

Conductance fluctuations reflect density-density and spin-spin correlations.

Theoretical analysis of the Kondo problem shows spatial charge and spin correlation patterns.

Identification of the Kondo cloud formation through tunneling conductance noise.

Abstract

Scanning tunneling miscoscopy is one of the most powerful spectroscopic tools for single-electron excitations. We show that the conductance fluctuations, or noise in the conductance, of a tunneling current into an interacting electron system is dominated by density-density and spin-spin correlations. This allows one to probe two-particle properties (susceptibilities) and collective excitations by standard experimental tunneling methods. We demonstrate this theoretically, using a novel many-body calculation for the multi-center Kondo problem, including both direct and indirect exchange between magnetic atoms. An example of the two-particle correlations around a single magnetic adatom in the Kondo regime, as would be viewed by a scanning tunneling microscope, is given. The spatial dependance of the charge and spin correlations, including the formation of the Kondo cloud in the spin sector, are shown.