Fast material handled by laser

A femtosecond light burst drives an exotic electronic transition into a semi-metallic crystal, an unprecedentedly fast time scale. Credit: © Beaulieu

Researchers from the Physics and Chemistry Department of the Fritz Haber Institute and the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg have learned that ultrafast switches in material properties can be triggered by laser pulses – and why. This knowledge may enable new transistor concepts.

Making the speed of electronic technology as fast as possible is a central goal of contemporary material research. The main components of fast computing technologies are transistors: switchgear devices that switch on and off electrical currents very quickly as basic steps of logic operations. To improve our knowledge of ideal transistor materials, physicists are constantly trying to determine new methods for performing such extremely fast switches. Researchers from the Fritz Haber Institute of the Max Planck Society in Berlin and the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg have now discovered that a new kind of ultrafast switch can be accomplished with light.

The physicists involved in the project are studying how best to obtain materials to change their properties – to make magnetic metals non-magnetic, for example, or to change the electrical conductivity of a crystal. Electrical properties of a material are strongly related to the arrangement of the electrons in the crystal. Controlling the arrangement of the electrons has been a key issue for decades. Most control methods, however, are quite slow.

“We knew that external influences such as temperature or pressure variations work,” says Dr. Ralph Ernstorfer, group leader in the Department of Physical Chemistry at the Fritz Haber Institute, “but that takes time, at least a few seconds.” Those who regularly use a smartphone or computer know that a few seconds can feel like an eternity. So Dr. Ernstorfer’s group explored how to change material properties much faster with light.

Using completely new equipment at the Fritz Haber Institute, the researchers massively reduced the switching time to just 100 femtoseconds by firing ultra-short optical laser pulses at their chosen material, a semi-metallic crystal composed of tungsten and telluric atoms. Bright light on the crystal prompts it to reorganize its internal electronic structure, which also changes the conductivity of the crystal. In addition, the scientists were able to observe exactly how its electronic structure changed.

“We used a new instrument to photograph the transition every step of the way,” explains Dr. Samuel Beaulieu, who worked as a postdoctoral fellow with Ralph Ernstorfer at the Fritz-Haber-Institut (2018-2020) and who is now a permanent researcher at the Center Lasers Intenses and Applications (CELIA) at CNRS-Bordeaux University. “This is amazing progress – we used to just know what the electronic structure of the material looks like, but never during the transition,” he adds. Moreover, cutting-edge modeling of this new process by Dr. Nicolas Tancogne-Dejean, Dr. Michael Sentef and Prof. Dr. Angel Rubio of the Max Planck Institute for the Structure and Dynamics of Matter has revealed the origin of this that new kind of ultrafast electronic transition. The laser pulse affecting the materials changes the way electrons interact with each other. That is the driving force of this exotic transition, called the Lifshitz transition.

This method is likely to generate a lot of knowledge about possible future transistor materials. The mere fact that light can drive ultrafast electronic transitions is a first step toward even faster and more efficient technology.

The study is published in Scientific Advances.


Researchers report changing material between semiconductors and metallic states


Additional information:
“Ultrafast Dynamic Lifshitz Transition”, Scientific Advances (2021). DOI: 10.1126 / sciadv.abd9275

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Quote: Ignite it: Rapid material manipulation by laser (2021, April 21) taken April 21, 2021 from https://phys.org/news/2021-04-fast-material-laser.html

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