Fragile 3D Order in V$_{1-x}$Mo$_x$O$_2$

TL;DR

This study uncovers a fragile 3D to 2D structural transition in V$_{1-x}$Mo$_x$O$_2$, driven by geometric frustration, with minimal impact on electronic properties, revealing complex interplay between structure and electron correlations.

Contribution

It reports the discovery of a novel 2D frustrated order emerging from a 3D phase in V$_{1-x}$Mo$_x$O$_2$, highlighting structural frustration effects.

Findings

Collapse of 3D order at x=0.17

Emergence of 2D frustrated order at x=0.19

Long-range correlations along (11L) planes with short-range transverse correlations

Abstract

The metal-to-insulator transition (MIT) in rutile VO$_2$ has proven uniquely difficult to characterize because of the complex interplay between electron correlations and atomic structure. Here we report the discovery of the sudden collapse of three-dimensional order in the low-temperature phase of V$_{1-x}$Mo$_x$O$_2$ at $x=0.17$ and the emergence of a novel frustrated two-dimensional order at $x=0.19$, with only a slight change in electronic properties. Single crystal diffuse x-ray scattering reveals that this transition from the 3D M1 phase to a 2D variant of the M2 phase results in long-range structural correlations along symmetry-equivalent (11L) planes of the tetragonal rutile structure, yet extremely short-range correlations transverse to these planes. These findings suggest that this two-dimensionality results from a novel form of geometric frustration that is essentially structural in origin.