One of the widely shared recent articles at Phys.org was
What's going on?
A normal crystal may have atoms or molecules at regularly spaced places (a lattice)\[
(x,y,z) \in \ZZ^3.
\] In some units or a coordinate system, the three coordinates are integer-valued. This setup breaks the group of spatial translations from the continuous group \(\RR^3\) to the discrete subgroup \(\ZZ^3\), assuming that the crystal is infinite. Now, Wilczek's general idea is that he wants the same "symmetry breaking" to be applied to the translations in time, too. Effectively, his new "material", the quantum time crystal, is doing something special – or reaching the maximum value of some observable – at moments \(t\in \ZZ\) in some units, too.