Crystal structures in slow motion

Laser manipulation can be used to alter the properties of materials in a very precise way. This principle is already widely used in technologies such as playback DVDs. However, the underlying processes usually occur at such rapid and small distances that they have so far prevented direct observation. Researchers at the University of Göttingen and the Max Planck Institute (MPI) for Biophysical Chemistry in Göttingen have now filmed, for the first time, a laser transformation of a crystal structure with a nanometer resolution and in slow motion. the electronic microscope. The results were published in the journal Science.

The team, which includes Thomas Danz and Professor Claus Ropers, took advantage of an unusual property material made up of thin atomic layers of sulfur and tantalum atoms. At room temperature, its crystal structure is transformed into small wavelike structures – a “cost density wave” is formed. At higher temperatures, phase transitions occur in which the original microscopic waves suddenly disappear. The electrical conductivity also varies greatly, an interesting effect for nano-electronics.

In their experiments, the researchers stimulated this phase shift with short laser pulses and recorded a film of cost-density wave reaction. “What we are seeing is the rapid creation and growth of tiny regions where the material has been adapted to the next stage,” explained first author Thomas Danz of the University of Göttingen. developed in Göttingen offers the highest time resolution for such images in the world today. “The unique feature of this experiment lies in a newly developed imaging technique, which is particularly sensitive to the specific changes observed in this phase motion. The Göttingen physics use it to construct images that are made up only of electrons dispersed by the strength of the crystal.

Their state-of-the-art method allows researchers to gain basic insights into structural changes with light. “We are already in a position to move our imaging approach to other crystal structures,” said Professor Claus Ropers, director of Nano-Optics and Ultrafast Dynamics at the University of Göttingen and Director at MPI for Biophysical Chemistry. “In this way, we will not only answer fundamental questions in solid-state physics, but we will also open up new perspectives for future optically transferable materials, intelligent nano-electronics. “

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Original publication: Thomas Danz et al., Ultrafast nanoimaging of the order parameter in structural phase motion, Science 2021, doi: 10.1126 / science.abd2774

Contact:

Thomas Danz

University of Göttingen

Faculty of Physics

Nano-Optics and Ultrafast Dynamics

Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Email: [email protected]

Professor Claus Ropers

University of Göttingen

Faculty of Physics

Nano-Optics and Ultrafast Dynamics

and the Max Planck Institute for Biophysical Chemistry – Ultrafast Dynamics

Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Phone: +49 (0) 551 39-24549

Email: [email protected]

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