It was only a matter of time.
A strange form of matter called a time crystal has appeared in two more types of materials, doubling the number of known time crystal habitats. In a typical crystal, its arrangement of atoms repeats regularly in space, like the alternating sodium and chloride ions that make up a salt crystal. But time crystal patterns repeat at regular time intervals.
A team of scientists has created a time crystal in a solid material called monoammonium phosphate, the researchers reported in Physical Review Letters Another team made their time crystal in a type of liquid containing star-shaped molecules, according to a study also published in Physical Review Letters.
Both time crystals rely on a quantum property called spin, which makes some atomic nuclei appear to spin like a top. In time crystals, the direction of that spin was at regular intervals.
Repeated pulses of radio waves were used to trigger the rotation of the spins. But even when the spins were not quite right, both materials maintained a regular pattern of release, revealing that they had a preferred timing structure.
Scientists created the only other two time crystals first known in 2016. One was made using defects in diamond; the other using a chain of ions, or electrically charged atoms, of the chemical element ytterbium.
Unlike the other known examples, the monoammonium phosphate time crystal was created in a solid material with an ordered physical structure - a traditional crystal. The other materials were disordered.
These curiosities are so new that scientists are still not sure what materials the crystals are found in, or if they have any practical use. Now the clock is ticking for the next discovery of a time crystal.
Source : Science News
J. Rovny, R.L. Blum and S.E. Barrett. Observation of discrete-time-crystal signatures in an ordered dipolar many-body system. Physical Review Letters Vol. 120, May 4, 2018, p. 180603. doi:10.1103/PhysRevLett.120.180603.
S. Pal et al. Temporal order in periodically driven spins in star-shaped clusters. Physical Review Letters Vol. 120, May 4, 2018, p. 180602. doi:10.1103/PhysRevLett.120.180602.
J. Rovny, R.L. Blum and S.E. Barrett. 31P NMR study of discrete time-crystalline signatures in an ordered crystal of ammonium dihydrogen phosphate. Physical Review B . Vol. 97, May 1, 2018, p. 184301. doi:10.1103/PhysRevB.97.184301.