Mechanically induced metal-insulator transition in carbyne

TL;DR

This study uses first-principles calculations and analytical models to show that mechanical strain and zero-point vibrations can induce a metal-insulator transition in carbyne by affecting its Peierls distortion, with potential applications in electromechanical devices.

Contribution

It demonstrates how mechanical strain and quantum vibrations jointly control the Peierls transition in carbyne, extending understanding of 1D metal-insulator transitions.

Findings

Peierls transition is enhanced under strain in carbyne.

Zero-point vibrations can suppress Peierls distortion in free chains.

Strain induces a transition from metallic to insulating state around 3% strain.

Abstract

First-principles calculations for carbyne under strain predict that the Peierls transition from symmetric cumulene to broken-symmetry polyyne structure is enhanced as the material is stretched. Interpretation within a simple and instructive analytical model suggests that this behavior is valid for arbitrary 1D metals. Further, numerical calculations of the anharmonic quantum vibrational structure of carbyne show that zero-point atomic vibrations alone eliminate the Peierls distortion in a mechanically free chain, preserving the cumulene symmetry. The emergence and increase of Peierls dimerization under tension then implies a qualitative transition between the two forms, which our computations place around 3% strain. Thus, zero-point vibrations and mechanical strain jointly produce a change in symmetry resulting in the transition from metallic to insulating state. In any practical realization, it is important that the effect is also chemically modulated by the choice of terminating groups. Our findings are promising for applications such as electromechanical switching and band gap tuning via strain, and besides carbyne itself, they directly extend to numerous other systems that show Peierls distortion.