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The remarkable material vanadiumdiselenide (VSe2) has some exciting properties in both 2D and 3D

A recent paper in Nano Letters describes a collaboration between researchers in South Korea, Scotland and the Aarhus-group led by Søren Ulstrup.

An ultra-short laser pulse triggers the phase transition in VSe2. Illustration from the paper.
An ultra-short laser pulse triggers the phase transition in VSe2. Illustration from the paper.

In the world of physics you can be a conductor, a semi-conductor or an isolator. If you cool an ultrathin layer of Vanadiumdiselenide below 135 K the material will be an isolator, but if you heat it, it behaves like a metal, and the change can occur lightning fast from one phase to the other. With a laser able to send ultra fast pulses (500 nanoseconds) a heating occurs, and with this the desired phase transition - but only if the layer has a thickness of one single atom. In thicker layers, that is when the material behaves as a 3D material, the behaviour is quite different.

This means that you can control electronic states with fast light pulses, and this can be used when building and operating electronic cirquits in nano-scale.

If the light pulse is considerably shorter, nothing happens. This is explained by the group of researchers to be due to a phase transition in the material where electrons and atomic nuclei interact. Had it been an interaction only between electrons, the response time would have been on the order of 10 femtoseconds. Thus the new paper at the same time reveals some basic theoretical properties of the exotic material, and aims at new practical uses in nano-electronics in the future.

Søren Ulstrup has given an interview in connection to the work in Scotland.

 Søren Ulstrup har givet et interview i forbindelse med arbejdet i Skotland. This interview gives a lot of deeper details, and is available here.

The paper is titled " Ultrafast Triggering of Insulator?Metal Transition in Two-

2 Dimensional VSe2", and can be downloaded from here.