A group of scientists from the Politecnico di Milano and the University of Rostock, Germany, has discovered a new kind of phase transition in a strange quasi-crystal caused by laser light. The discovery was published recently in the famous journal Nature.
Scheme of an artificial quasi-crystal with laser light. Light from a laser propagates in optical fibers whose special arrangement interweaves different light paths, so that the laser light mimics the quantum motion of electrons in a quasi-crystal. Image Credit: Politecnico di Milano.
The observations could lead the way for all-inclusive learning of the internal functioning of engineered or complex materials and their use in modern phase-controlled materials-based applications.
The discovery of this new phase transition in quasi-crystals represents a breakthrough in the understanding of some fundamental phenomena of quantum matter. It may also pave the way for the development of a new technology and type of material unlike anything we have seen before, the properties of which we will be able to simultaneously control and modify at will.
Stefano Longhi, Physics Department, Politecnico di Milano
“It would be a new form of matter much more flexible and controllable than the one we currently know about,” added Stefano Longhi.
A prime example of phase transition is seen in winter where small alterations from a temperature of 0 °C determine whether water is present in its liquid state or as solid snow or ice. Less noticeable, and thus less recognizable, transitions also exist.
These transitions are present among matter forms (or phases) that could be equally significant to the functioning of several commonly utilized devices — from computer chips to cell phones: for example, the ability or inability of a material to conduct electricity, or to transfer particles or energy with the neighboring environment.
With advanced optical technologies, the experimental team recently made a quasi-crystal of light (quasi-crystals are structures that are imperfectly ordered, such as crystals, but not fully disordered and belong to the rarest structures present in nature) and established that seemingly autonomous features in this strange material are, indeed, closely linked and can together experience sudden change.
To study the features of these bizarre materials, a quasi-crystal was emulated in the lab with laser light, which propagates in kilometer-long optical fibers in an intertwined manner. The quantum motion of electrons in the quasi-crystal is closely mirrored by the complicated dynamics of light in such fibers.
A triple phase transition was found during the light propagation study in these systems. In this transition, the conductivity, topological properties and energy exchange between the quasi-crystal and its environment change suddenly but at the exact same time.
Journal Reference:
Weidemann, S., et al. (2022) Topological triple phase transition in non-Hermitian Floquet quasicrystals. Nature. doi.org/10.1038/s41586-021-04253-0.