TU Dortmund University researchers synchronize distant time crystals
- Researchers discovered that multiple time crystals inside a semiconductor can synchronize their electron-nuclear spin oscillations across distances of up to 40 micrometers.
- Alex Greilich at TU Dortmund University, a new study published in Nature Communications details how these exotic physical systems lock to a common frequency through the coupling of...
- The experiments build on prior research conducted in January 2024, when physicists at TU Dortmund University demonstrated that a continuous time crystal could persist inside a semiconductor with...
Synchronization of Spatially Separated Time Crystals
Researchers discovered that multiple time crystals inside a semiconductor can synchronize their electron-nuclear spin oscillations across distances of up to 40 micrometers.
Led by Prof. Alex Greilich at TU Dortmund University, a new study published in Nature Communications details how these exotic physical systems lock to a common frequency through the coupling of spin-polarized electrons, operating much like pendulum clocks falling into the same rhythm.
Gallium Arsenide Lattices at Ultra-Low Temperatures
The experiments build on prior research conducted in January 2024, when physicists at TU Dortmund University demonstrated that a continuous time crystal could persist inside a semiconductor with oscillations stable for hours.
The time crystals form inside a semiconductor made from gallium arsenide containing small amounts of indium and silicon. These added elements create localized electrons within the material lattice. At temperatures close to -270 °C, each electron interacts with roughly one million nearby nuclear spins.
Laser Excitation and Spin Polarization Feedback
To initiate the synchronization process, researchers use a pump laser to align the electron spins, which then transfer their polarization to the surrounding nuclear spins.
When a weak magnetic field is applied, the polarization of those nuclear spins begins to rotate in a sustained rhythm. Feedback between the electron and nuclear spins keeps the oscillations going, while a second laser allows scientists to monitor how the oscillations develop over time.
Overcoming Microscopic Variations with Broad Illumination
Different regions of the semiconductor are not perfectly identical at the microscopic level, meaning time crystals forming in separate areas would normally oscillate at slightly different frequencies due to local variations.
However, when researchers illuminate many regions at once with a broad laser beam, the separate oscillations lock together and operate at the same frequency.
Huygens’ Pendulum Principle on a Microscopic Scale
The effect draws comparison to an observation made by Christiaan Huygens in 1665 involving two pendulum clocks that gradually synchronized because of weak mechanical interaction transmitted through a shared support.
In the semiconductor, the connection operates differently, relying on the movement of spin-polarized electrons rather than mechanical vibrations.
The 40-Micrometer Threshold and Future Networks
The research team found that time crystals located as far as 40 micrometers apart could still synchronize, a distance more than one thousand times greater than the characteristic size of a single oscillator.
Once the separation exceeds that threshold, the individual time crystals no longer lock together and instead continue oscillating independently. The findings demonstrate non-local coupling between spatially separated spin systems, which could help lay the groundwork for future networks of controllable spin oscillators and potential spin-based technologies.