Metal-insulator transition in quasi-one-dimensional HfTe3 in the few-chain limit

TL;DR

This study investigates how reducing HfTe3 to few-chain and single-chain forms induces a metal-insulator transition, revealing chain spiraling and structural distortions that open an energy gap.

Contribution

It provides experimental and theoretical evidence of a size-driven metal-insulator transition in HfTe3 at the few-chain limit, including chain spiraling and structural distortions.

Findings

Chains spiral about each other at the triple-chain limit

A trigonal anti-prismatic distortion opens an energy gap

Size reduction induces a metal-insulator transition

Abstract

The quasi-one-dimensional linear chain compound HfTe3 is experimentally and theoretically explored in the few- to single-chain limit. Confining the material within the hollow core of carbon nanotubes allows isolation of the chains and prevents the rapid oxidation which plagues even bulk HfTe3. High-resolution transmission electron microscopy combined with density functional theory calculations reveals that, once the triple-chain limit is reached, the normally parallel chains spiral about each other, and simultaneously a short-wavelength trigonal anti-prismatic rocking distortion occurs that opens a significant energy gap. This results in a size-driven metal-insulator transition.