Conductance through atomic point contacts between fcc(100) electrodes of gold

TL;DR

This study uses density functional theory to analyze how electrical conductance varies in gold nanocontacts with different atomic configurations, revealing the conditions for true one-atom contacts and conductance oscillations.

Contribution

It provides detailed insights into conductance evolution and channel behavior in gold atomic point contacts, emphasizing the atomic structure's role in conductance properties.

Findings

Conductance decreases from ~3 G_0 to ~1 G_0 with elongation.

True one-atom contact with a single open channel requires an atom with coordination number 2.

Longer contacts exhibit conductance oscillations and gaps due to electron state oscillations.

Abstract

Electrical conductance through various nanocontacts between gold electrodes is studied by using the density functional theory, scalar-relativistic pseudopotentials, generalized gradient approximation for the exchange-correlation energy and the recursion-transfer-matrix method along with channel decomposition. The nanocontact is modeled with pyramidal fcc(100) tips and 1 to 5 gold atoms between the tips. Upon elongation of the contact by adding gold atoms between the tips, the conductance at Fermi energy E_F evolves from G ~ 3 G_0 to G ~ 1 G_0 (G_0 = 2e/h^2). Formation of a true one-atom point contact, with G ~ 1 G_0 and only one open channel, requires at least one atom with coordination number 2 in the wire. Tips that share a common vertex atom or tips with touching vertex atoms have three partially open conductance channels at E_F, and the symmetries of the channels are governed by the wave functions of the tips. The long 5-atom contact develops conductance oscillations and conductance gaps in the studied energy range -3 < E-E_F < 5 eV, which reflects oscillations in the local density of electron states in the 5-atom linear "gold molecule" between the electrodes, and a weak coupling of this "molecule" to the tips.