Distant Time Crystals Oscillate in Unison Inside a Semiconductor

Physicists at TU Dortmund University have shown that continuous time crystals inside a semiconductor can synchronize with one another over surprisingly large distances, locking billions of spin oscillators into a shared rhythm . The finding, published in Nature Communications by the group of Prof. Alex Greilich, extends earlier work that demonstrated a continuous time crystal whose oscillations remained stable for hours . The new result 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 frequency .

This discovery matters because it provides a concrete platform for controllable networks of spin oscillators, which could advance several spin-based technologies, including spin networks, spin-wave computing, and other collective-spin information-processing platforms . The team created the crystals in a semiconductor made of indium gallium arsenide (InGaAs), a material already central to modern electronics and optoelectronics .

The Material: Indium Gallium Arsenide at 3 K

The team used a 10‑µm‑thick layer of indium gallium arsenide containing 3% indium, doped with silicon . The material acts as a host for billions of independent spin systems. Localized electrons around the silicon donors each interact with about one million surrounding nuclear spins through the hyperfine interaction, forming the core of each time-crystal oscillator . The experiment was conducted at approximately −270 °C (3 K), a cryogenic temperature required to maintain coherence in the spin system .

How the Oscillators Synchronize

The synchronization mechanism is conceptually similar to the one Christiaan Huygens observed in pendulum clocks hanging from a common beam: weak coupling through the shared medium pulls the oscillations into unison . In this case, a broad pump laser about 200 µm wide excites many regions of the semiconductor simultaneously. The otherwise independent oscillations in each region lock to a common frequency . This is not a trivial effect, because each oscillator naturally oscillates at a slightly different frequency due to local variations in the material .

The experimental confirmation came from a two-laser test. The team used two separate pump lasers to excite two independent regions of the semiconductor, monitored by a single broad probe beam. At a 25‑µm spacing, region 1 oscillated at 91 mHz and region 2 at 69 mHz—a difference of about 27%. When both pumps were turned on simultaneously, the two peaks collapsed into a single peak at 80 mHz, confirming mutual synchronization. At 50‑µm separation, the original two frequencies remained distinct, showing the range limit of the coupling .

The Range and Tolerance of Synchronization

Time crystals separated by up to 40 µm could synchronize, a distance more than 1,000 times the characteristic size of an individual oscillator . More precisely, the measured synchronization range was 38 ± 3 µm between beam centers, or 25 ± 3 µm edge-to-edge after accounting for beam profiles .

Remarkably, synchronization held even when the natural frequencies of distant oscillators differed by as much as 40% . This wide tolerance to frequency mismatch is a signature of strong coupling and indicates that the mechanism is robust enough to overcome intrinsic disorder in the material.

The Coupling Mechanism: Spin Diffusion

The team identified spin-polarized electrons diffusing through the material as the information-bearing carriers that mediate the synchronization. The estimated spin-diffusion length is about 17 µm, derived from a diffusion constant of roughly 24 cm²/s and a spin relaxation time of about 120 ns . This length scale matches the observed synchronization range. Nuclear spin diffusion and electron hopping were ruled out as the coupling mechanism because they are too slow or too short-ranged to account for the effect .

Why This Matters for Future Technologies

The ability to synchronize continuous time crystals over macroscopic distances opens a path toward building networks of spin oscillators that can be controlled and read out optically. Because the semiconductor platform is already a mature technology, integrating these time crystals into devices is more practical than with many other quantum systems .

Potential future applications include spin networks for information transfer, spin-wave computing schemes that use collective spin excitations, and other collective-spin information-processing platforms . The TU Dortmund team's demonstration that these crystals can synchronize even when their natural frequencies differ by up to 40% suggests that the approach is robust enough for practical implementation.

The Broader Context of Time Crystal Research

These results build on a series of advances from the same group. In January 2024, Greilich's team created a continuous time crystal in the same material system that lasted for at least 40 minutes—10 million times longer than previous demonstrations—with no observed decay . A follow-up study in March 2025 explored the nonlinear dynamics of such time crystals under periodic driving, revealing phenomena ranging from perfect synchronization to chaotic behavior within a single semiconductor structure .

The synchronization of multiple time crystals reported in this Nature Communications paper extends the conceptual reach of time crystals from isolated curiosities to potentially useful building blocks for spin-based technologies .