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How important are "time crystals"?


A hypothetical object called a time crystal was first proposed by Frank Wilczek in 2012. Once just a mathematical curiosity, its existence may have been experimentally confirmed by a team of physicists who observed predicted time crystal behavior in an interacting spin chain of trapped atomic ions. The work is reported in a pre-print submitted to arXiv in September 2016.

Initially, many doubted that such quantum systems could exist for the unusual property of periodic motion in the ground state. Like ordinary crystals which form repeating patterns in the crystal structure created by spontaneous translational symmetry breaking in three dimensions, time crystals extend to the fourth dimension: time. Observing time crystals would imply observing the breaking of time translation symmetry. Time crystals exhibit repetition (crystalline behavior) in both space and time, and the growth of repeating lattices in time does not consume nor produce any energy despite of perpetual motion in the ground state.

But the required spontaneously broken time translation symmetry had not been observed before, and the lack of a precise definition for time crystals created difficulty in the past for realizing such a physical system. Previously, researchers showed that when they considered both the ground state and states in thermal equilibrium, time translation symmetry could not be broken.

Later, another team, using the idea of a non-equilibrium driven system, showed time translation symmetry can be spontaneously broken in a large class of many-body-localized driven systems with discrete time translation symmetry. A paper on this work titled Floquet Time Crystals was published on August 2016 in Phys. Rev. Lett. The preprint version on arXiv has been cited 9 times as of question writing, as reported by Google Scholar.

Will this paper have at least 9 more citations, by the end of 2016?

Certainly, the discovery has large implications in the understanding of states of matter in both equilibrium and non-equilibrium systems. It also implies observing time translation symmetry being spontaneously broken for the first time.

More citations mean that the paper is achieving greater scientific impact, and this is part of an ongoing small-scale experiment to look at predictions of paper citation rates on various timescales.

For the question to resolve positively, a Google Scholar search must report a minimum of 18 citations of the paper Floquet Time Crystals on or before Dec 31st, 2016.

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