Vanadium dioxide’s weird phase transition just got weirder

Date: Nov 2, 2018

For the first time, researchers have gotten a detailed view of how atoms in a compound called vanadium dioxide move when an ultrafast laser pulse transforms the material from an electrical insulator to a conductor — and it’s nothing like scientists expected.

Rather than switching from one crystal formation to another in a direct, synchronized manner, like choreographed ballerinas, the atoms shift around in a disordered manner, more like clumsy partygoers doing the Cha Cha Slide. This new insight into the inner workings of vanadium dioxide, reported in the Nov. 2 Science, may inform engineers who are trying to harness the dual nature of the compound and others like it for new technologies.

Scientists have been fascinated for decades by the nature of vanadium dioxide’s insulator-to-metal transition, which happens when the material is heated above about 67° Celsius or hit with an ultrafast laser pulse. But that electrical about-face is difficult to study, because it happens in about 150 femtoseconds, or quadrillionths of a second.

Other experiments that involved tickling vanadium dioxide’s atoms with laser light have measured only the average motions of atoms during this transformation. These general trends suggested a smooth shift from one crystal formation to another, but were not detailed enough to reveal small deviations in the atoms’ movement.

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