Physicists at TU Dortmund University have shown that continuous time crystals can synchronize with one another across surprisingly large distances inside a semiconductor. The finding, reported in Nature Communications, extends earlier work from the same team, which demonstrated a time crystal whose oscillations remained stable for hours. The new experiment reveals that these exotic oscillators do not have to operate independently: under the right conditions, multiple time crystals can lock together and share a common rhythm.
Time crystals are unusual physical systems that exhibit repeating internal motion even when they are not being exposed to a periodically varying external force. In an ordinary crystal, atoms are arranged in a repeating pattern through space. A time crystal displays an analogous form of order in time, with some internal property—such as spin, magnetization, or particle motion—oscillating at a stable frequency. Continuous time crystals are particularly remarkable because their periodic behavior persists rather than occurring only in response to a sequence of timed pulses.
The Dortmund team creates these oscillators in a semiconductor made from gallium arsenide, with small quantities of indium and silicon added to tailor its electronic properties. At temperatures close to −270 degrees Celsius, the material contains localized electrons whose spins interact with the spins of roughly one million surrounding atomic nuclei. Spin is a quantum-mechanical form of angular momentum, and although it is not a tiny ball literally rotating, it behaves in many experiments like a magnetic needle that can point in different directions.
The process begins with a laser pulse that aligns, or polarizes, the spins of the localized electrons. Through their magnetic interaction, the electrons transfer part of this polarization to the surrounding nuclear spins. When the system is placed in a weak magnetic field, the nuclear spins begin to precess, meaning that their orientations rotate around the field direction. The electron spins respond to this changing nuclear environment, and the feedback between the two spin populations can sustain a remarkably stable oscillation. A second laser allows researchers to monitor the resulting dynamics without directly disturbing the system in the same way as the initial excitation.
The semiconductor is not perfectly uniform at the microscopic level. Small variations in the local composition and environment mean that different regions naturally prefer slightly different oscillation frequencies. If each region is excited separately, the resulting time crystals can drift out of step with one another. Yet the researchers found that a broad laser beam, illuminating many regions at once, changes this behavior. Instead of maintaining their individual frequencies, the oscillators begin to adjust to one another and settle into a shared rhythm.
This process is known as synchronization, a phenomenon found throughout physics and biology. Mechanical clocks can synchronize through vibrations transmitted by a common support, as Christiaan Huygens famously observed in the seventeenth century. Fireflies can flash together, and networks of neurons can produce coordinated activity. In the semiconductor experiment, however, the coupling mechanism is neither mechanical nor electrical in the conventional sense. It is mediated by the movement—or diffusion—of spin-polarized electrons through the material.
As polarized electrons diffuse away from one localized region, they carry information about the spin state of that region into its surroundings. When they reach another time crystal, they can influence its electron-spin polarization and therefore its oscillation frequency and phase. The phase describes where an oscillator is within its cycle at a given moment. Small interactions gradually bring the phases and frequencies closer together, allowing separate oscillators to behave as a coordinated network rather than as isolated quantum systems.
The researchers report that time crystals separated by distances of up to approximately 40 micrometers can synchronize. That distance is more than one thousand times the characteristic size of an individual oscillator, making the effect strikingly non-local on the scale of the microscopic structures involved. Beyond the maximum range over which the polarized electrons can diffuse effectively, the time crystals continue oscillating but no longer lock to one another. The result therefore identifies a physical boundary for the synchronization network, determined by the transport of spin information through the semiconductor.
The discovery provides a new way to study collective dynamics in driven and dissipative quantum materials. Although the time crystals are not powered by a periodic clock-like signal, lasers are needed to prepare and observe the semiconductor, and energy is exchanged with the surrounding environment. Their stable oscillations emerge from a balance between optical pumping, spin interactions, diffusion, and relaxation. Understanding how these competing processes produce long-lived collective order could help researchers design controllable arrays of spin oscillators. Such systems may eventually contribute to spin-based information technologies, where information is encoded and transported using spin rather than electrical charge. For now, the experiment offers a vivid demonstration that time crystals can do more than keep time alone: they can communicate, coordinate, and form extended communities of synchronized quantum oscillators.
Subject of Research: Not applicable
Article Title: Non-local synchronization of continuous time crystals in a semiconductor
Web References: https://doi.org/10.1038/s41467-026-75714-1
References: Nature Communications, DOI: 10.1038/s41467-026-75714-1
Image Credits: Alex Greilich
Keywords
Time crystals, continuous time crystals, quantum physics, semiconductor physics, spin dynamics, electron spins, nuclear spins, synchronization, spin diffusion, quantum materials
