Physicists at TU Dortmund University showed in January 2024 that a continuous time crystal could persist inside a semiconductor, with its oscillations remaining stable for hours. Now, in a new study published inNature Communications, Prof. Alex Greilich and his colleagues have found that multiple time crystals can emerge within the same material and synchronize their electron-nuclear spin oscillations.
Time crystals are unusual physical systems whose internal behavior repeats in a regular rhythm over time, even though they are not being driven by a repeating external signal.
In the TU Dortmund experiments, the time crystals form inside a semiconductor made from gallium arsenide with small amounts of indium and silicon. These added elements create localized electrons within the material. At temperatures close to -270 °C, each electron interacts with roughly one million nearby nuclear spins.
To initiate the process, the researchers use a pump laser to align the electron spins. The electrons 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.
Feedback between the electron spins and nuclear spins keeps the oscillations going. A second laser allows the researchers to monitor how those oscillations develop over time.
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