A unique crystal of space-time consists of magnons (quasiparticles corresponding to the elementary excitation of a system of interacting spins) at room temperature. Using a Maxymus scanning transmission X-ray microscope at Bessy II at the Helmholtz Center in Berlin, scientists have removed a repeating periodic structure of magnetization in a crystal.

A crystal is a solid whose atoms or molecules are regularly arranged in a certain structure. If you look at it through a microscope, you can find an atom or a molecule always at regular intervals. It is like crystals of space-time: in which a repeating structure exists not only in space, but also in time. The smallest components are constantly in motion until, after a certain period, they return to their original state.

In 2012, Nobel Prize winner in physics Frank Wilczek discovered the symmetry of matter in time. He is considered the discoverer of these so-called time crystals, although as a theorist he predicted them only hypothetically. Since then, several scientists have searched for material in which this phenomenon is observed. The fact that spacetime crystals do exist was first confirmed in 2017. However, the structures were only a few nanometers in size, and they formed only at very low temperatures below –250°C. The fact that scientists have now succeeded in displaying relatively large space-time crystals a few micrometers in size on video at room temperature is considered groundbreaking. But also because they were able to show that their time-space crystal of magnons can interact with other magnons that collide with it.

“We took a regularly repeating structure of magnons in space and time, sent out more magnons, and they eventually scattered. Thus, we were able to show that the time crystal can interact with other quasiparticles. No one has yet been able to show this directly in an experiment, let alone a video.”

Nick Treger, PhD student at the Max Planck Institute for Intelligent Systems

In their experiment, the scientists placed a strip of magnetic material on a microscopic antenna through which they passed RF current. This microwave field produced an oscillating magnetic field, a source of energy that stimulated the magnons in a strip – a spin wave quasiparticle. Magnetic waves migrated to the left and right stripes, spontaneously condensing into a repeating pattern in space and time. Unlike trivial standing waves, this pattern was formed even before two converging waves could meet and intersect. A pattern that regularly disappears and reappears on its own must be a quantum effect.

The uniqueness of the discovery is also in the use of an X-ray camera, which not only allows one to see the wave fronts with a very high resolution, which is 20 times better than the best light microscope. But it can even do it at up to 40 billion frames per second, as well as with extremely high sensitivity to magnetic phenomena.

“We were able to show that such spacetime crystals are much more reliable and widespread than anticipated. Our crystal condenses at room temperature, and particles can interact with it, unlike an isolated system. Moreover, it has reached a size that could be used to do something with this magnonic crystal of spacetime. This could lead to many potential uses.”

Pavel Grushetsky, scientist from the Faculty of Physics, Adam Mickiewicz University in Poznan

Classic crystals have a very wide range of applications. Now, if crystals can interact not only in space but also in time, scientists can add another dimension to possible applications. The potential for communications technology, radar and imaging technology is enormous.