Utrecht researchers make space-time crystal out of sodium atoms

Image: The red-yellow lines show the space-time crystal at different times. The light beam illustrates how x-rays would be diffracted by the crystal. The sharp peaks on the projection screen give the experimental evidence that the structure is indeed a crystal in both space as well as time.

Crystals, such as salt, sugar and ice, have a self-repeating structure in space and are very common in everyday life. Time crystals have a self-repeating structure in time and have only recently been made for the first time in materials that consist of a large number of small magnets. Utrecht researchers have for the first time succeeded in combining these two types of crystals in a droplet of sodium atoms that has been cooled down to the almost absolute zero of temperature. The researchers are publishing their results today in Physical Review Letters.

At such a low temperature, the droplet forms a so-called superfluid in which the atoms can move without experiencing friction. This prevents the space-time crystal from melting and ensures that it can exist for a long time. Since the researchers use a non-magnetic fluid, the work shows that space-time crystals can not only occur in magnetic materials. In addition, the work is of fundamental importance for the study of new phases of matter and may eventually lead to the creation of so-called atomic lasers with unusual temporal properties.

Publication

Observation of a Space-Time Crystal in a Superfluid Quantum Gas
J. Smits, L. Liao, H. T. C. Stoof, and P. van der Straten
Physical Review Letters, 2018, Editor’s suggestion