Physicists Directly Image Space-Time Crystal
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Space-time crystals are time-periodic self-organized structures postulated by the Nobel laureate in physics Frank Wilczek in 2012. In new research, physicists from Germany and Poland transferred this concept to quasiparticles called magnons and experimentally demonstrated a space-time crystal at room temperature; they also directly imaged it using a scanning transmission X-ray microscope.

“We took the regularly recurring pattern of magnons in space and time, sent more magnons in, and they eventually scattered,” said first author Nick Träger, a doctoral student at the Max Planck Institute for Intelligent Systems.

“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 in a video.”

In their experiment, Träger and colleagues 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, a source of energy that stimulated the magnons in the strip.

Magnetic waves migrated into the strip from left and 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 regularly disappears and reappears on its own, must therefore be a quantum effect.

Träger et al. experimentally demonstrated a driven space-time crystal at room temperature: (a) sketch of the sample with one magnonic permalloy (Py) stripe and a coplanar waveguide; (b) snapshot of a time-resolved scanning transmission X-ray microscopy movie; the gray scale represents the mz component; (c) phase and amplitude map at fcw after FFT in time through each pixel of the scanning transmission X-ray microscopy movie; the color code shows the amplitude and phase information. Image credit: Träger et al., doi: 10.1103/PhysRevLett.126.057201.

“Not only can it make the wavefronts visible with very high resolution, which is 20 times better than the best light microscope,” said Dr. Gisela Schütz, also from the Max Planck Institute for Intelligent Systems.

“It can even do so at up to 40 billion frames per second and with extremely high sensitivity to magnetic phenomena as well.”

“We were able to show that such space-time crystals are much more robust and widespread than first thought,” said co-author Dr. Pawel Gruszecki, a scientist in the Faculty of Physics at the Adam Mickiewicz University.

“Our crystal condenses at room temperature and particles can interact with it — unlike in an isolated system.”

“Moreover, it has reached a size that could be used to do something with this magnonic space-time crystal. This may result in many potential applications.”

“Classical crystals have a very broad field of applications,” said senior author Dr. Joachim Gräfe, also from 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 for communication, radar or imaging technology is huge.”

The results were published in the journal Physical Review Letters.

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Nick Träger et al. 2021. Real-Space Observation of Magnon Interaction with Driven Space-Time Crystals. Phys. Rev. Lett 126 (5): 057201; doi: 10.1103/PhysRevLett.126.057201

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