Conductance Quantization and Electron Resonances in Sharp Tips and Atomic-Size Contacts

TL;DR

This paper theoretically investigates atomic-size contacts, revealing that narrow s-like metal contacts exhibit stable resonant states at the Fermi energy, explaining conductance quantization and its dependence on contact size.

Contribution

It introduces a self-consistent tight-binding model to analyze resonant states and conductance quantization in atomic-scale contacts, highlighting the role of contact size and disorder.

Findings

Resonant states are localized in the neck region of narrow contacts.

Conductance quantization is explained by these resonant states.

Resonant properties diminish as contact size increases.

Abstract

The electronic and transport properties of atomic-size contacts are analyzed theoretically using a self-consistent tight-binding model. Our results show that, for s-like metals, a sufficiently narrow contact exhibits well defined resonant states at the Fermi energy, spatially localized in the neck region. These states are robust with respect to disorder and provide a simple explanation for the observed tendency to conductance quantization. It is also shown that these properties disappear for a sufficiently large contact area. The possible relevance of this resonant states in scanning tunneling spectroscopy using sharp tips is briefly analized.