With all the recent speculation about time crystals, perhaps it’s time to really scrutinize the info and facts. A time crystal is a unique crystal which has an atomic structure that repeats in both space and time, which means that it is in a state of constant oscillation without energy.
According to researchers, it is now possible to measure these crystals; two teams of scientists claim to have already created time crystals in a lab. Their findings would prove that a previously unknown phase of matter exists.
In short, metals and insulators are in equilibrium, but it has long been suspected that other states could exist in the Universe. As per head researcher Norman Yao:
“This is a new phase of matter, period, but it is also really cool because it is one of the first examples of non-equilibrium matter. For the last half-century, we have been exploring equilibrium matter, like metals and insulators. We are just now starting to explore a whole new landscape of non-equilibrium matter.”
As mentioned, the idea of time crystals has been around for a while. In 2012, Nobel-Prize winning theoretical physicist Frank Wilczek argued that time crystals are structures that have movement at their lowest energy state, known as a ground state.
This is referred to as the zero-point energy of a system, and many believe that this state cannot exist because energy would need to be expended somehow. However, Wilczek predicted that time crystals have a structure that repeats in both time and space, which would keep them oscillating in ground state. So, a time crystal is similar to endlessly oscillating jelly in the natural ground state, and this characteristic is what makes it new, non-equilibrium matter.
Now, Yao has devised a blueprint to outline precisely how to make and measure time crystals; he can even predict what various phases around the time crystals should be. Indeed, the solid, liquid, and gas phases have all been mapped. Yao says that his paper in the journalPhysical Review Letters is, “the bridge between the theoretical idea and the experimental implementation.” One of the teams involved in the recent studies was from the University of Maryland, and the other was from Harvard; both teams have created time crystals, and virtually all the details can be found at arXiv.org (here and here). What’s more, the University of Maryland’s time crystals were created by way of a conga line of 10 ytterbium ions (with entangled electron spins).
The ions needed to be kept out of equilibrium, so the researchers targeted them with two different lasers. The first laser generated a magnetic field, and the second laser altered the spins of the atoms. As a result of the spins of the atoms becoming entangled, the atoms settle into a stable, repetitive pattern of spin flipping (which is what defines a crystal). The system must break time symmetry in order to be a time crystal, and observing the ytterbium atom conga line is used to detect these oddities.
Yao asked:
“Wouldn’t it be super weird if you jiggled the Jell-O and found that somehow it responded at a different period? But that is the essence of the time crystal. You have some periodic driver that has a period ‘T’, but the system somehow synchronises so that you observe the system oscillating with a period that is larger than ‘T’.”
Time crystals change phases under different magnetic fields and laser pulsing, similar to how an ice cube melts.
The Harvard time crystal is unique because it was setup using densely packed nitrogen vacancy centers in diamonds:
“Such similar results achieved in two wildly disparate systems underscore that time crystals are a broad new phase of matter, not simply a curiosity relegated to small or narrowly specific systems,” argues Phil Richerme from Indiana University. “Observation of the discrete time crystal . . . confirms that symmetry breaking can occur in essentially all natural realms, and clears the way to several new avenues of research.”
Again, these blueprints have been published in Physical Review Letters, the Harvard time crystal paper can be referenced here, and the University of Maryland paper can be scrutinized here.