Chemistry Reference
In-Depth Information
Chapter 9
Metallic Nanowires on the Atomic Scale:
Correlation Between Structure, Electronic
Properties, and Electronic Transport
H. Pfnür
Abstract
One-dimensional (1D) properties with strong electron correlation and
various instabilities have been found recently in metallic chains or ribbons gener-
ated by metal adsorption of sub-monolayers on insulating substrates like Si(111)
or Si(557). The unavoidable coupling to 2D and 3D for all these cases results
in a wealth of new phenomena. Here we concentrate on the Pb/Si(557) system,
where these couplings in 2D and 3D become very obvious, and discuss structural
self-stabilization as the origin of 1D electronic transport. Finally, a new 1D state
generated by step decoration is described and its properties are discussed.
9.1 Introduction
One-dimensional electronic systems have attracted great interest recently because
of their exotic electronic properties. These comprise quantization of conductance,
charge density waves (CDW), spin-density waves (SDW) [
1
] triplet superconduc-
tivity, and Luttinger-liquid behavior [
2
]. Properties of electrons related to charge
and spin may be separated in a quasiparticle picture [
3
]. As a consequence, low-
dimensional systems, and in particular 1D chains, exhibit a variety of instabilities
with a wealth of associated phase transitions. Especially 1D metallic chains should
undergo a Peierls instability accompanied by a significant change of the conductivity
due to a metal-insulator transition. In the classical picture, electron-phonon inter-
action drives CDW formation (Peierls instability) and the opening of a band gap at
the Fermi surface [
4
]. Apart from interesting physical properties, new perspectives
of potential applications of metallic quantum wires in context with molecular elec-
tronics and nanoscale interconnects [
5
], nanoscale devices, or optical waveguides
[
6
] are expected.
Metallic wires exceeding the length of a few atoms cannot be suspended freely,
i.e., they have to be embedded into a 2D or 3D environment causing inevitably 2D or
