The laws of quantum mechanics allow for the existence of 'quasi-particles':
excitations in materials that behave exactly like ordinary particles. A
major advantage of quasi-particles over ordinary particles is that their
properties can be engineered. In a Nature Materials News & Views article
this week, IoP physicist Erik van Heumen describes recent experiments where
even the interactions between quasi-particles can be tuned.
In recent years, the mathematical branch of topology, studying the shapes of
things, and the physical branch of condensed matter physics, studying the
behaviour of solids and fluids, have merged into an exciting new research
field: that of topological materials. One of the most exciting aspects of
this combined field is the emergence of exotic quasi-particles: local
disturbances in materials that behave exactly like particles. That such
quasi-particles can exist, was already known from the quantum description of
simple materials. What the combination with topology offers is a whole new
set of such particles, known for example as Dirac and Weyl fermions, axions
and magnetic monopoles.
Engineering interactions
Freeing themselves from the strict rules for ordinary particles dictated by
nature, researchers gain control over the properties of quasi-particles by a
careful choice of the materials used to generate them. One wish that has
been high on the list has been to find materials in which the type and
strength of interactions between quasi-particles can be tuned.
Recently, a family of materials was discovered that feature atoms arranged
in a so-called kagome lattice. In his 'News & Views' article, Erik van
Heumen describes experiments, reported on in the latest edition of Nature
Materials, that suggest the formation in these materials of a so-called
'flux-density wave', an excitation that provides the first confirmation of
the theoretical predictions that these materials could host exotically
interacting quasi-particles. The fact that such tunable interactions between
quasi-particles in materials can now be created in the laboratory holds
great promise for future studies of topological materials.
Reference:
Kagome lattices with chiral charge density, Nature Materials (2021).
DOI: 10.1038/s41563-021-01095-z
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