Matter can apparently organise itself in a way nobody had seen in a solid before. Physicists have detected a three-dimensional woven pattern inside a crystal. Their work appeared in the journal Light: Science & Applications.
The find came in a ferroelectric material. Such crystals form regions in which the electric charges all point the same way. These regions respond to electric fields and to mechanical pressure. That is why ferroelectric crystals sit inside sensors and capacitors today.
The team cooled a sample of potassium lithium tantalate niobate, KTN:Li for short. Below 18.8 degrees Celsius the material forms the regions typical of such crystals, the German science portal wissenschaft.de reports. This time something else happened. Fine threads appeared and crossed one another at regular intervals. At the crossing points they alternated above and below, like the threads in a woven fabric.
The crystal stayed hard throughout. The group measured no deformation. The weave holds as long as the temperature stays two to eight degrees below the ferroelectric transition point.
A green laser untangles the fabric
The structure can be altered deliberately. A tightly focused green laser beam dissolves the weave locally and leaves a layered order behind, the science site Phys.org reports. The rest of the crystal is untouched. Warm the sample and cool it again, and the weave returns, though in a new pattern.
Three groups worked on the study. They were led by Eugenio Del Re of Sapienza University in Rome, Feifei Xin of Nankai University in Tianjin and Aharon J. Agranat of the Hebrew University of Jerusalem, joined by colleagues at the University of Groningen. Agranat had originally grown the crystals for optical switching, giving them periodic variations in chemical composition along the way.
What the discovery is good for remains open. Topologically protected data storage that can be read and changed with light is conceivable, the researchers write. For now their interest is the physics behind it. Because the weave arises through spontaneous symmetry breaking, they suspect similar structures in liquid crystals, superconductors and quantum materials. "Sometimes nature is far more creative than our theories predict," Xin says.