# Scanning Tunneling Shot Noise Spectroscopy in Kondo Systems

## TL;DR

This paper uses advanced theoretical methods to analyze shot noise and Fano factor measurements in Kondo systems, revealing their bias dependence and interference effects, which can serve as sensitive probes of Kondo screening and quantum interference.

## Contribution

It introduces a theoretical framework combining large-N and Keldysh formalisms to interpret scanning tunneling shot noise spectroscopy data in Kondo systems, highlighting the Fano factor's sensitivity to correlation and interference effects.

## Key findings

- Fano factor exhibits bias dependence similar to Kondo resonance in conductance.
- Interference effects can enhance or suppress the Fano factor.
- Correlation between differential conductance and Fano factor suggests new experimental tests.

## Abstract

Using a large-N theory in combination with the Keldysh non-equilibrium Greens function formalism, we investigate the current, differential conductance, zero-frequency shot-noise and Fano factor as measured by scanning tunneling shot noise spectroscopy (STSNS) using a scanning tunneling microscope (STM) near single Kondo impurities and in Kondo lattices. We show that the Fano factor $F$ exhibits a characteristic bias dependence arising from Kondo screening that is similar to the Kondo resonance observed in the differential conductance. Moreover, the lineshape of $F$ is strongly dependent on the ratio of the tunneling amplitudes for electron tunneling from the STM tip into the conduction band and electronic levels of the magnetic adatoms. We demonstrate that the Fano factor can be enhanced or suppressed due to interference effects and as such, is not only a sensitive probe for the correlation effects arising from Kondo screening, but also for quantum interference between tunneling electrons. We identify a correlation between the form of the differential conductance and the Fano factor that could be tested in future STSNS experiments.