Physicists develop a very robust time crystal

A team from TU University Dortmund recently succeeded in producing a very durable time crystal that lived millions of times longer than had been shown in previous experiments. In doing so, they corroborated an extremely interesting phenomenon, postulated around ten years ago by Nobel Prize winner Frank Wilczek and which had already found its place in science fiction films.

The results were published in Natural physics.

Crystals, or to be more precise, crystals in space, are periodic arrangements of atoms on large scales. This arrangement gives the crystals their fascinating appearance, with smooth facets like those of precious stones.

As physics often treats space and time on the same level, for example in special relativity, Frank Wilczek, a physicist at the Massachusetts Institute of Technology (MIT) and Nobel Prize winner in physics, postulated in 2012 that in more than crystals in space, there must also be crystals in time.

For this to be the case, he says, one of their physical properties would have to spontaneously begin to change periodically over time, even if the system does not experience corresponding periodic interference.

The possibility of such time crystals was the subject of controversial scientific debate for several years, but it did not take long to arrive in movie theaters: for example, a time crystal played a central role in the Avengers film : Endgame (2019) from Marvel Studios.

Since 2017, scientists have indeed succeeded on several occasions in demonstrating a potential time crystal. However, these were systems which, contrary to Wilczek’s original idea, are subjected to temporal excitation with a specific periodicity, but then react with another period twice as long.

A crystal that behaves periodically over time, although the excitation is time independent, i.e. constant, was only demonstrated in 2022 in a Bose-Einstein condensate. However, the crystal only lived for a few milliseconds.

Dortmund physicists led by Dr. Alex Greilich have designed a special crystal made of indium gallium arsenide, in which nuclear spins serve as a reservoir for the time crystal. The crystal is continuously illuminated so that a nuclear spin polarization is formed by interaction with the electronic spins. And it is precisely this nuclear spin polarization which then spontaneously generates oscillations, equivalent to a time crystal.

The current state of experiments is that the lifespan of the crystal is at least 40 minutes, or 10 million times longer than what has been demonstrated so far, and that it could potentially live much longer .

It is possible to vary the crystal period over wide ranges by systematically modifying the experimental conditions. However, it is also possible to move to areas where the crystal “melts”, that is, loses its periodicity.

These areas are also interesting because chaotic behaviors, which can be maintained over long periods of time, are then manifested.

This is the first time that scientists can use theoretical tools to analyze the chaotic behavior of such systems.