Physicists at TU Dortmund University in Germany have shown that so-called time crystals embedded in a semiconductor chip can lock into a shared rhythm even when separated by tens of micrometers, a distance more than a thousand times the size of a single time crystal itself.
The findings, published in Nature Communications, extend earlier work by the same group, led by physicist Alex Greilich, which first showed continuous time crystals, systems that oscillate in a steady pattern without needing regular pulses of outside energy to keep going, persisting in a semiconductor in 2024. The new experiments show that when several of these oscillating systems form at different spots on the same chip, they do not always run independently: under the right conditions, they pull each other into synchrony.
The time crystals in this study arise from the interaction between electrons and roughly a million surrounding atomic nuclei inside a semiconductor made of indium gallium arsenide, cooled to about -270 degrees Celsius, nearly absolute zero. A laser pulse aligns the spins of localized electrons, and a weak magnetic field sets off a slow, self-sustaining rotation of the nuclear spins, the oscillation that defines the time crystal. The researchers measured synchronization between time crystals separated by up to 38 ± 3 micrometers, with the effect vanishing beyond that range, and found that oscillators pulled into sync even when their natural frequencies initially differed by a significant margin.
Electrons carry the signal
The team traced the coupling to spin-polarized electrons drifting between the two oscillating regions, rather than to any direct magnetic or optical link, evidence, the authors say, that the synchronization travels farther than the electrons' own localized "home" region would suggest. The researchers compare the behavior to a phenomenon first described in 1665, when Dutch scientist Christiaan Huygens noticed that two pendulum clocks mounted on the same wall would gradually fall into an identical rhythm, weakly coupled through vibrations in the wood.
Time crystals were first proposed as a theoretical curiosity a little over a decade ago and have since been realized in a range of physical systems, from trapped ions to superconducting circuits. Showing that they can synchronize across measurable distances inside an ordinary semiconductor, a platform already used throughout the electronics industry, suggests the effect could eventually be harnessed rather than merely observed, as summarized in ScienceDaily's coverage of the paper.
The authors say the next step is to test whether the coupling between time crystals can be switched on and off deliberately, for instance by applying an electric field to control how electrons drift across the chip. If that proves possible, networks of synchronized spin oscillators could serve as building blocks for spintronic devices or analog computing hardware that stores and processes information in patterns of spin rather than conventional electrical charge.
