In January 2024, physicists at TU Dortmund University demonstrated a continuous time crystal in a semiconductor whose oscillations remained stable for hours. In a new study published in Nature Communications , Prof. Alex Greilich and his team show that many such time crystals can form in the same material and synchronize their electron-nuclear spin oscillations.
Time crystals are systems whose internal dynamics repeat periodically in time without being driven by a periodic external signal. In the TU Dortmund experiment, they are created in a semiconductor made of gallium arsenide containing small amounts of indium and silicon, which provides localized electrons. At temperatures close to −270 °C, each electron interacts with about one million surrounding nuclear spins.
A pump laser aligns the electron spins, which transfer their polarization to the nuclear spins. In a weak magnetic field, the nuclear-spin polarization begins to rotate. The resulting feedback between the electron and nuclear spins sustains the oscillations, while a second laser is used to observe them.
Because the microscopic environment varies across the semiconductor, individual regions normally oscillate at slightly different frequencies. However, when a broad laser beam excites many regions simultaneously, their oscillations lock to a common frequency.
This synchronization resembles Christiaan Huygens’ famous observation of two pendulum clocks in 1665. The clocks synchronized through weak mechanical coupling in their shared support. In the semiconductor, the coupling is instead produced by the diffusion of spin-polarized electrons.
The researchers found that time crystals separated by up to 40 micrometers can synchronize, more than one thousand times the characteristic size of an individual oscillator. At larger distances, they continue to oscillate independently.
The results demonstrate non-local coupling between spatially separated spin systems and may provide a foundation for controllable networks of spin oscillators in future spin-based technologies.
Nature Communications
Experimental study
Not applicable
Non-local synchronization of continuous time crystals in a semiconductor
22-Jul-2026
The authors declare no competing interests.