Conductance quantisation in metallic point contacts

TL;DR

This paper reviews the quantum conductance properties of atomic-scale metallic point contacts, emphasizing experimental techniques, observations, and theoretical models, including recent advances and unique atomic geometries like gold chains.

Contribution

It provides a comprehensive overview of experimental and theoretical methods for studying conductance quantisation in metallic point contacts, highlighting recent developments and novel atomic configurations.

Findings

Observation of conductance quantisation in metallic point contacts

Identification of shell effects in sodium nanowires

Analysis of atomic chain formations in gold contacts

Abstract

The electrical transport properties of atomic-scale conductors are reviewed, with an emphasis on the relations of this problem with studies on quantum size effects in metallic clusters. A brief introduction is given of the natural formalism for discussing electron transport in ballistic conductors: the Landauer theory. After introducing the experimental techniques, which are used for studying ballistic point contacts in metals, the experimental observations for the conductance of atomic-scale contacts are presented. In order to obtain a full description in terms of the quantum modes for conductance, several recently developed techniques are reviewed, which go beyond straightforward measurement of the conductance. A brief discussion is given of an unusual atomic geometry for gold contacts, which evolve into a chain of freely suspended atoms. Then shell filling effects in sodium nanowires are discussed in the context of the influence of the conductance modes on the total energy of the system. The chapter ends with an outlook on promising new developments.