Shot-noise measurements of single-atom junctions

TL;DR

This paper presents a novel apparatus for measuring shot noise in single-atom junctions using a scanning tunneling microscope at liquid helium temperatures, enabling detailed noise analysis at the atomic scale.

Contribution

The authors develop and demonstrate a local shot-noise measurement system integrated with a STM, overcoming technical challenges in single-atom noise measurements.

Findings

Successful shot-noise measurements in single-atom junctions.

Reduced thermal noise and input capacitance through a broadband amplifier.

Maintained full STM capabilities during noise measurements.

Abstract

Current fluctuations related to the discreteness of charge passing through small constrictions are termed shot noise. This unavoidable noise provides both advantages - being a direct measurement of the transmitted particles' charge, and disadvantages - a main noise source in nanoscale devices operating at low temperature. While better understanding of shot noise is desired, the technical difficulties in measuring it result in relatively few experimental works, especially in single-atom structures. Here we describe a local shot-noise measurement apparatus, and demonstrate successful noise measurements through single-atom junctions. Our apparatus, based on a scanning tunneling microscope operates at liquid helium temperatures. It includes a broadband commercial amplifier mounted in close proximity to the tunnel junction, thus reducing both thermal noise and the input capacitance that limit traditional noise measurements. The full capabilities of the microscope are maintained in the modified system and a quick transition between different measurement modes is possible.