Origin of the Metal-Insulator Transition of Indium Atom Wires on Si(111)

TL;DR

This study uses first-principles calculations to reveal that the metal-insulator transition in indium wires on Si(111) is driven by a structural phase change involving bond rearrangements, not by a charge-density wave mechanism.

Contribution

It provides an atomistic understanding of the phase transition, identifying it as a first-order process driven by lattice reconstruction rather than Peierls instability.

Findings

The phase transition involves bond-breaking and bond-making processes.

The transition is first-order with an energy barrier.

The metal-insulator change is due to lattice reconstruction, not CDW formation.

Abstract

As a prototypical one-dimensional electron system, self-assembled indium (In) nanowires on the Si(111) surface have been believed to drive a metal-insulator transition by a charge-density-wave (CDW) formation due to electron-phonon coupling. Here, our first-principles calculations demonstrate that the structural phase transition from the high-temperature 4x1 phase to the low-temperature 8x2 phase occurs through an exothermic reaction with the consecutive bond-breaking and bond-making processes, giving rise to an energy barrier between the two phases as well as a gap opening. This atomistic picture for the phase transition not only identifies its first-order nature but also solves a long-standing puzzle of the origin of the metal-insulator transition in terms of the x2 periodic lattice reconstruction of In hexagons via bond breakage and new bond formation, not by the Peierls instability-driven CDW formation.