Quantum properties of atomic-sized conductors

TL;DR

This paper reviews the quantum properties of atomic-sized metallic contacts, highlighting experimental techniques, quantum effects in conductance and mechanical properties, and their significance in mesoscopic physics research.

Contribution

It provides a comprehensive review of experimental and theoretical advances in understanding quantum effects in atomic-scale metallic contacts over the past decade.

Findings

Observation of conductance quantization in nanowires

Quantum effects in mechanical properties like force and cohesion energy

Correlation between atomic structure and electronic transport phenomena

Abstract

Using remarkably simple experimental techniques it is possible to gently break a metallic contact and thus form conducting nanowires. During the last stages of the pulling a neck-shaped wire connects the two electrodes, the diameter of which is reduced to single atom upon further stretching. For some metals it is even possible to form a chain of individual atoms in this fashion. Although the atomic structure of contacts can be quite complicated, as soon as the weakest point is reduced to just a single atom the complexity is removed. The properties of the contact are then dominantly determined by the nature of this atom. This has allowed for quantitative comparison of theory and experiment for many properties, and atomic contacts have proven to form a rich test-bed for concepts from mesoscopic physics. Properties investigated include multiple Andreev reflection, shot noise, conductance quantization, conductance fluctuations, and dynamical Coulomb blockade. In addition, pronounced quantum effects show up in the mechanical properties of the contacts, as seen in the force and cohesion energy of the nanowires. We review this reseach, which has been performed mainly during the past decade, and we discuss the results in the context of related developments.