I Time rondeau crystals, experimental observations

[Astronuc]

A relative asked me about the following article: Experimental observation of a time rondeau crystal
https://www.nature.com/articles/s41567-025-03028-y

Abstract​

Conventional phases of matter can be characterized by the symmetries they break, one example being water ice whose crystalline structure breaks the continuous translation symmetry of space. Recently, breaking of time-translation symmetry was observed in non-equilibrium systems, producing so-called time crystals. Here we investigate different kinds of partial temporal ordering, stabilized by non-periodic yet structured drives, which we call the rondeau order. Using carbon-13 nuclear spins in diamond as a quantum simulator, we use microwave driving fields to create tunable short-time disorder in a system exhibiting long-time stroboscopic order. Our spin control architecture allows us to implement a family of driving fields including periodic, aperiodic and structured random drives. We use a high-throughput read-out scheme to continuously observe the spin polarization and its rondeau order, with controllable lifetimes exceeding 4 s. Using degrees of freedom associated with the short-time temporal disorder of rondeau order, we demonstrate the capacity to encode information in the response of observables. Our work broadens the landscape of observed non-equilibrium temporal order, and raises the prospect for the potential applications of driven quantum matter.

I pointed my relative to following article: Scientists Discovered a Time Crystal That Reveals a New Way to Order Time
https://www.yahoo.com/news/articles/scientists-discovered-time-crystal-reveals-180055389.html

Time crystals, first predicted by US theoretical physicist Frank Wilczek in 2012 before being observed for the first time in 2016, bring additional complexity to the patterned atomic matrix that makes up regular solids.

. . .

A time crystal describes particles moving through sequences that aren't dictated by the timing of any external push, breaking the expected flow. The particles oscillate within their lowest energy states with a timing pattern that repeats; that pattern can also be perfectly superimposed, like the spatial arrangement of atoms in a crystal.

A time quasicrystal is one in which the oscillations of the atoms are structured, but do not repeat, like a Penrose tiling – a pattern in dimensional space that never quite repeats, yet still follows a set of rules.

According to Moon and his colleagues, a time rondeau crystal is yet another version, exhibiting both order and disorder, repeating and not repeating, like the musical form known as a rondeau.

This area is outside of my regular experience. I'm interested in radiation effects in polycrystalline material, i.e., grain boundaries as well as vacancies, which "are lattice sites where an atom should sit, but nothing is there," and interstitials. Ions, electrons, neutrons and gammas cause atomic displacements assuming sufficient energy, and overtime, a solid crystal will accumulate a populations of vacancies and interstitials, which tend to saturate at a given fluence (particles per unit area) or cumulative displacements.

Does anyone at PF work in this area of time crystals or time rondeau crystals?

 

[TensorTronic-270]

The papers Di Chen1,Jing Wang2,, Tianyi Chen1 & Lin Shao1,2("Defect annihilation at grain boundaries in alpha-Fe") is highly relevant to your interest, as it specifically investigates the fundamental, atomic-scale mechanisms of how grain boundaries handle radiation-induced vacancies and interstitials in a typical structural material (alpha-iron, α-Fe).

This study directly addresses your questions about the role of these defects in materials exposed to high fluence (measured by displacements per atom, or dpa ) and offers an atomic explanation for why these defects do not necessarily saturate the grain boundary sink sites.

Here is a summary of the key findings from this paper:

1. Grain Boundaries as Efficient, Non-Saturating Defect Sinks
The paper reinforces the idea that grain boundaries (GBs) act as defect sinks that trap and recombine radiation-induced point defects. The major discovery is that this process is mediated by new, transient defect structures, which makes the GBs more effective than previously understood.

Self-Healing Mechanism: Nanograined metals are studied as potential "self-healing materials" because of their high density of grain boundaries, which promote the recombination of point defects.

Non-Saturating Sinks: The study proposes that grain boundaries act as highly efficient defect sinks that cannot saturate under extreme radiation conditions because the annihilation process involves continuous energy-minimization and defect transformation, rather than simply filling a fixed number of sites.

Irradiation Conditions: The research focuses on the conditions found in fission reactors, where materials are exposed to high fluence neutrons and accumulate radiation damage up to a few hundred displacements per atom (dpa).

2. The Role of Chain-Like Defects in Annihilation
The study, which used Molecular Dynamics (MD) simulations, discovered that the defect-boundary interactions are not simply defects moving individually to the GB for annihilation. Instead, the process is mediated by transient, chain-like defects:

Chain-Like Defects (BC and GBC): The interactions are always mediated by the formation and annealing of chain-like defects, which consist of alternately positioned interstitials and vacancies.

Effective Transport: These chain defects allow a point defect to effectively "translate large distances" to annihilate with its opposite (i.e., an interstitial moving to a vacancy, or vice versa). This process realizes an equivalent transport from one end of the chain to the other.

Governing Factor: The landing points of these chain defects on the boundary always correspond to sites having the lowest defect formation energies. The location of these energy-minimum sites is determined by the specific grain boundary configuration.

They could be worth a read.