Quasi-particles with adjustable interactions

The laws of quantum mechanics allow the existence of “quasi-particles”: excitations in materials that behave exactly like ordinary particles. A major advantage of quasiparticles over ordinary particles is that their properties can be changed. In a Natural materials In this week’s News & Views article, IoP physicist Erik van Heumen describes recent experiments where even interactions between quasiparticles can be tuned.

In recent years, the mathematical branch of topology, studying the forms of things, and the physics branch of condensed matter physics, studying the behavior of solids and fluids, have merged into an exciting new area of ​​research: 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, magnetic axions and monopoles.

Engineering interactions

Breaking free from the strict rules of ordinary particles dictated by nature, researchers have mastered the properties of quasi-particles by carefully choosing the materials used to generate them. One wish that featured high on the list was to find materials in which the type and strength of interactions between quasiparticles can be tuned.

Recently, a family of materials has been discovered that features atoms arranged in what is called a kagome lattice. In his article ‘News & Views’, Erik van Heumen describes experiences, reported in the latest edition of Natural materials, which suggest the formation in these materials of a ‘flux density wave’, an excitation which provides the first confirmation of the theoretical predictions according to which these materials could harbor quasi-particles in exotic interaction. 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.

Provided by the University of Amsterdam