Aarhus University Seal / Aarhus Universitets segl

No metallic transitional phase in VO2

New paper in Physical Review X with co-author IFA's Simon Wall

Locked transitional phases in VO2. Illustration from the paper.
Locked transitional phases in VO2. Illustration from the paper.

The IFA-research group Ultrafast Dynamics of Quantum Materials has a recent paper titled "Does VO2 host a transient monoclinic metallic phase?" published in Physical Review X. 

Short popular summary from Phys. Rev.:

 

Light-induced phase changes in solids offer a new way to manipulate and probe materials. In this technique, ultrashort laser pulses rapidly excite electrons in the solid, triggering a quick localized temperature change. Many such experiments have claimed the emergence of novel transient states of matter, however identifying these phases often requires combining several different techniques. Here, we show that heating differences between techniques can incorrectly suggest different behaviors, thus introducing systematic errors to experiments.

To study these effects, we reexamine a claim of a light-induced transient metallic phase in the material vanadium dioxide. By comparing optical and x-ray dynamics across a wide range of timescales—from femtoseconds to seconds—we determine that heat plays a key role in this transition. When heating is accounted for, we find a single phase transition and no evidence for an alleged “hidden” transient phase.

Given the wide applicability of these techniques to many other solids, our results show that a full understanding of the thermal state is needed to interpret other claims of light-induced transient states of matter.