What Do You Know About Time Crystals - The Newest State Of Matter?

If you are still used to the good old 4 fundamental states of matter (Solid, Liquid, Gas and Plasma), you are sooo last year!

While there are a multitude of other non-classical states (glass, liquid crystals, Bose–Einstein condensate,...), time crystals is a new state of matter whose existence has only been proven earlier this year 2017 (experiments at end of 2016 to be exact), 5 years after being speculated by MIT professor Frank Wilczek in 2012.

I was in fact so intrigued finding out about them, that I decided to do an in-depth research and share it with you :)

What are those time crystals?

A Crystal (not time crystal) is basically a solid, containing atoms or molecules that are arranged in a highly ordered and periodic/repeated manner.
Table salt, diamonds, and snow flakes are examples of such crystals.

Microscopic View of Crystallite (Crystal) structure vs Polycristalline (exhibiting mutiple different crystals combined, including most metals) vs Amorphous (anything else without periodic atom arrangement)

Microscopic cubic arrangement of Halite Crystal NaCl: Na+(purple) Cl-(green) (Salt)

While crystals are essentially space crystals, meaning they are well ordered and repeated in space - 3D, time crystals just added the 4th "Time" dimension and hence dubbed Time Crystals

Basically, time crystals are similarly ordered and repeated in space, yet they would additionally switch their configurations in a repeating pattern through time, hence flipping from one configuration to another back and forth.

Breaking time-translation symmetry

Time-translation symmetry is basically a fundamental mathematical hypothesis of modern physics, stating that laws of physics are the same everywhere and across time.
Normal Crystals break symmetry in space, since depending on the location, their atoms might behave differently, but also conservation of momentum does not necessarily apply.
Check out the Umklapp process illustration below whereby to the left this is the normal result, to the right U-process is where the momentum is modified and hence symmetry is broken.

This lead Wilczek back in 2012 to consider breaking time-translation symmetry via the concept of time crystals. With the creation of time crystals, time-translation symmetry is now broken, due to the created oscillations within time crystals and the relevant change of arrangement over time.

This is best explained by Norman Yao, of UC Berkeley, whose blueprint paper in 2016 concerning lab-creating a time crystal paved the way to the successful creation of the first time crystals in late 2016/ early 2017, who illustrates them as close to the example of the act of jumping a rope. Every time your hand spins, you expect the rope to make a full rotation. Yet in the case of time crystals though, while the arm goes around twice, the rope only goes around once.

Do they break the laws of thermodynamics?

While time crystals do not break the laws of thermodynamics per se, due to the fact that throughout the full "activity" of their system there is preservation of energy, yet within the different stages of their oscillations and as the electrons would move irrelevant of the driving force (further details in experiments below) - back to breaking time symmetry, this might be considered as loss of energy. The system does exhibit a zero energy behavior, which leads us to the next notion..

Did we find a perpetual-motion system?

While this was one of the original claims by Wilczek, yet it was later proven that time crystals cannot exist in equilibrium (as proven by Masaki Oshikawa, university of Tokyo) and that essentially any matter cannot exist, at its ground state, in non-equilibrium.
Essentially, time crystals need constant motivation or a driving mechanism such as simulation by laser (more on creating time crystals below). In the absence of such simulation, time crystals would become dormant.

How were time crystals created?

Two different experiments around end of 2016, lead to the creation of time crystals.

The first was led by Christopher Monroe at University of Maryland, who relying on Yao's proposal, trapped 10 ytterbium ions as a chain (see picture below) and alternately applied laser pulses to create a magnetic field, another laser was also used to repetitively cause a partial flip to the spins of the atoms. This caused oscillations in the system, which were actually happening at half the frequency of the laser pulses. Hence the observation of time crystals. They key to maintaining the system was though to maintain the ions out of equilibrium, hence the exact notion of non-equilibrium time crystal.

chain of ytterbium ions utilized for creating the time crystal system

The second later experiment, led by Mikhail Lukin at Harvard, used a diamond crystal loaded with nitrogen vacancy centers, and a microwave for the pulses, similar results as the prior experiment were observed with half frequency oscillations compared to the microwave pulses, with the former lasting above one hundred cycles before the system went dormant. Hence the second generation of the time crystals.

Diamond time crystal system

Hope you found this as intriguing as I did! And thank you for reading through :)

@mcfarhat

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