Symmetry-Breaking Phase Transition without Peierls Mechanism in Conducting Monoatomic Chains

TL;DR

This study investigates a phase transition in monoatomic chains on a surface, revealing a symmetry-breaking transition that is not driven by the traditional Peierls mechanism but involves complex interchain interactions.

Contribution

It demonstrates a symmetry-breaking phase transition in 1D atomic chains without the Peierls instability, highlighting substrate-mediated interchain coupling effects.

Findings

Second-order phase transition at 585 K

Charge ordering with atomic displacements

Absence of electronic charge density wave signatures

Abstract

The one-dimensional (1D) model system Au/Ge(001), consisting of linear chains of single atoms on a surface, is scrutinized for lattice instabilities predicted in the Peierls paradigm. By scanning tunneling microscopy and electron diffraction we reveal a second-order phase transition at 585 K. It leads to charge ordering with transversal and vertical displacements and complex interchain correlations. However, the structural phase transition is not accompanied by the electronic signatures of a charge density wave, thus precluding a Peierls instability as origin. Instead, this symmetry-breaking transition exhibits three-dimensional critical behavior. This reflects a dichotomy between the decoupled 1D electron system and the structural elements that interact via the substrate. Such substrate-mediated coupling between the wires thus appears to have been underestimated also in related chain systems.