A title that seems worthy of an SF movie, and yet … A team of researchers has succeeded in creating a time-scale (spatio-temporal) crystal of micrometric size – made up of magnons at room temperature – and to film its behavior using a microscope ultra-precise X-ray. This is the very first time in the world that a recurring periodic magnetization structure has been filmed.
It is a German-Polish research team that is at the origin of this real technical feat. The researchers created a time crystal the size of a micrometer, made of magnons at room temperature, then using the Maxymus scanning transmission X-ray microscope at Helmholtz Zentrum Berlin, they were able to film the magnetizing structure periodic recurring in the crystal.
A crystal is a solid whose atoms or molecules are regularly arranged in a particular structure. If we look at the arrangement under a microscope, we discover an atom or a molecule always at the same intervals. The same is true for space-time crystals: however, the recurring structure exists not only in space, but also in time. The smaller components are constantly in motion until after a while they rearrange themselves into the original pattern.
A revolutionary discovery
In 2012, Nobel laureate in physics Frank Wilczek discovered the symmetry of matter in time. He is believed to be the discoverer of these so-called time crystals, although as a theorist he predicted them only hypothetically.
Since then, several scientists have looked for materials in which the phenomenon could be observed. The true existence of spatio-temporal crystals was first confirmed in 2017. However, the structures in question were only a few nanometers in size and only formed at very cold temperatures, below –250 degrees Celsius. .
The fact that the German-Polish team of researchers has now succeeded in imaging relatively large spatio-temporal crystals (a few micrometers) at room temperature is therefore considered revolutionary. The prowess also lies in the fact that they were able to show that their temporal crystal, made up of magnons, can interact with other magnons that meet it.
An exceptional experience
” We took the steadily recurring pattern of magnons in space and time, sent more magnons, and they eventually dispersed. Thus, we were able to show that the temporal crystal can interact with other quasiparticles. No one has yet been able to show it. directly in an experiment, and even less in video Says Nick Träger, PhD student at the Max Planck Institute for Intelligent Systems, lead author of the publication alongside Pawel Gruszecki.
In their experiment, Gruszecki and Träger placed a strip of magnetic material on a microscopic antenna through which they sent a radio frequency current. This microwave field triggered an oscillating magnetic field, an energy source that stimulated the magnons in the band (the quasi-particle of a spin wave). Magnetic waves migrated through the band from left to right, spontaneously condensing into a recurring pattern in space and time. Unlike trivial standing waves, this pattern was formed before the two converging waves could even meet and interfere. The pattern, which disappears and reappears regularly, must therefore be a quantum effect.
Gisela Schütz, Director of the Max Planck Institute for Intelligent Systems, which heads the Department of Modern Magnetic Systems, underlines the uniqueness of the X-ray camera used: “ Not only can it make the wavefronts visible with very high resolution, which is 20 times better than the best optical microscope. It can even do so at up to 40 billion images per second and with extremely high sensitivity to magnetic phenomena “.
” We have been able to show that these spatio-temporal crystals are much more robust and widespread than initially thought. Says Pawel Gruszecki, scientist at the Faculty of Physics at Adam Mickiewicz University in Poznań. ” Our crystal condenses at room temperature and particles can interact with it – unlike an isolated system. In addition, it reached a size that could be used for concrete applications “.
” Conventional crystals have a very wide field of applications. Now, if crystals can interact not only in space but also in time, we add another dimension to the possible applications. The potential of communications, radar or imaging technologies is enormous », Concludes Joachim Gräfe, former head of a research group in the Department of Modern Magnetic Systems and co-author of the study.