For the first time, physicists have captured a puzzling situation on video.
Using a scanning transmission X-ray microscope, the research team recorded the oscillations of a time crystal made of magnons at room temperature. This, they said, is a major breakthrough in the study of time crystals.
“We have been able to show that such spacetime crystals are much more robust and widespread than originally 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. Moreover, it has reached a size that could be used to do something with this magnonic space-time crystal. This could result in many possible applications.” “
Time crystals, sometimes referred to as space-time crystals, which were only confirmed to exist a few years ago, are just as fascinating as the name suggests. They look a lot like normal crystals, but for an extra quality.
In ordinary 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 repeating grids may differ in configuration, but they do not move much within a given formation: they only repeat spatially.
In time crystals, the atoms behave a little differently. They oscillate, rotating first in one direction and then in the other. These oscillations – also called ‘ticks’ – are locked at a regular and specific frequency. So where the structure of ordinary crystals repeats in space, in time crystals repeats in space and time.
To study time crystals, scientists often use ultra-cold Bose-Einstein condensates of magnon quasiparticles. Magnons are not real particles, but consist of a collective excitation of the spin of electrons – like a wave propagating through a grid 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 that allowed them to send a radio frequency current.
That current produced an oscillating magnetic field on the strip, with magnetic waves moving towards it from both ends; these waves stimulated the magnons in the strip and these moving magnons then condensed into a repeating pattern.
“We took the recurring pattern of magnons in space and time, sent more magnons in and they eventually spread,” said Träger. “This allowed us to demonstrate that the time crystal can interact with other quasi-particles. No one has been able to demonstrate this directly in an experiment, let alone in a video.”
The video above shows the magnetic wave front propagating through the strip, filmed at up to 40 billion frames per second using the MAXYMUS X-ray microscope at the BESSY II synchrotron radiation facility in Helmholtz Zentrum Berlin in Germany.
Time crystals must be stable and coherent over long periods of time, because they – theoretically – oscillate at their lowest possible energy state. The team’s research shows that powered magnonic time crystals can be easily manipulated, opening 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 broad field of application,” says physicist Joachim Gräfe of the Max Planck Institute for Intelligent Systems.
“If crystals can now interact not only in space but also in time, we will add another dimension of possible applications. The potential for communication, radar or imaging technology is enormous.”
The research is published in Physical Review Letters