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For the first time, physicists have captured an enigmatic state of matter on video.
Using a transmission scanning x-ray microscope, the research team recorded the oscillations of a temporal crystal made up of magnons at room temperature. This, they said, is a significant advance in the study of time crystals.
“We were able to show that these spatio-temporal crystals are much more robust and widespread than first thought,” said physicist Pawel Gruszecki of Adam Mickiewicz University in Poland.
“Our crystal condenses at room temperature and particles can interact with it – unlike an isolated system. Plus, it grew to a size that could be used to do something with this magnonic space-time crystal. This can lead to many potential applications. “
Time Crystals, sometimes also referred to as Space-Time Crystals, and only confirmed to exist a few years ago, are as fascinating as their name suggests. They look a lot like normal crystals, but for an added property.
In regular crystals, the constituent atoms are arranged in a fixed three-dimensional grid structure – think of the atomic lattice of a diamond or quartz crystal. These repetitive networks may differ in configuration, but within a given formation they do not move much: they only repeat themselves spatially.
In time crystals, atoms behave a little differently. They oscillate, turning first in one direction, then in the other. These oscillations – called “ticking” – are locked on a regular and particular frequency. Thus, where the structure of regular crystals repeats in space, in time crystals repeat in space and time.
To study the crystals of time, scientists often use ultra-cold Bose-Einstein condensates of magnon quasi-particles. Magnons are not real particles, but consist of a collective excitation of the spin of electrons – like a wave that propagates through a network of spins.
The research team led by Gruszecki and his colleague, physics doctoral student Nick Träger from the Max Planck Institute for Intelligent Systems in Germany, did something different. They placed a strip of magnetic permalloy on an antenna through which they could send a radio frequency current.
This current produced an oscillating magnetic field across the tape, with magnetic waves traveling over both ends; these waves stimulated the magnons in the strip, and these moving magnons then condensed into a repeating pattern.
“We took the steadily recurring pattern of the magnons in space and time, sent more magnons and they eventually dispersed,” said Träger. “So 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 in a video.”
The video above shows the magnetic wavefront propagating through the tape, filmed at up to 40 billion frames per second using the MAXYMUS X-ray microscope at the BESSY II synchrotron radiation facility at Helmholtz Zentrum Berlin in Germany.
Time crystals need to be stable and consistent over long periods of time because they – theoretically – oscillate at their lowest possible energy state. The team’s research shows that entrained magnonic time crystals can be easily manipulated, opening up a new way to reconfigure time crystals. This could open the state of matter to a range of practical applications.
“Classical crystals have a very wide field of application,” said physicist Joachim Gräfe of the Max Planck Institute for Intelligent Systems.
“Now, if crystals can interact not only in space but also in time, we add another dimension of possible applications. The potential of communication, radar or imaging technology is enormous.”
The research was published in Physical examination letters.
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