“Imagine a clock that will keep perfect time forever, even after the heat-death of the universe. This is the “wow” factor behind a device known as a “space-time crystal,” a four-dimensional crystal that has periodic structure in time as well as space.”
A group of scientists, spearheaded by researchers from the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have suggested an idea for the design of a space time crystal which is based on an electric field ion trap and the Coulomb repulsion of particles that carry the same electrical charge. According to Faculty scientist Xiang Zhang, “The electric field of the ion trap holds charged particles in place and Coulomb repulsion causes them to form a spatial ring crystal”. This concept of a crystal that has a distinct place in time had earlier been suggested by Nobel-prize winning physicist Frank Wilczek, who gave proof that the crystal can be created but its construction and implementation still remain vague. Zhang and his group, which included co-authors of a paper titled “Space Time Crystals of Trapped Ions”. On that team were Tongcang Li, Zhe-Xuan Gong, Zhang-Qi Yin, Haitao Quan, Xiaobo Yin, Peng Zhang and Luming Duan. They developed a crystal which is distinct in both space and time. The process of crystallization occurs when heat is withdrawn from a molecular system until a lower energy state is attained. Then a given point of lower energy, continuous spatial symmetry breaks down and the crystal takes up a separate symmetry, which means that instead of the structure being the same in all directions, it is the same in only a few directions. Following the blueprint designed by Zhang and Li and their colleagues, a spatial ring of trapped ions in constant rotation will periodically reproduce itself in time, which will eventually give form to a temporary analogue of an ordinary spatial crystal. “While a space-time crystal looks like a perpetual motion machine and may seem implausible at first glance”, Li says, “keep in mind that a superconductor or even a normal metal ring can support persistent electron currents in its quantum ground state under the right conditions”. Xiang Zhang believes that it might even be possible now to make a space-time crystal using their design and highly developed ion traps.