Quasi-particles with tunable interactions

Water waves are localized excitations within water that behave in many ways like particles. They have velocities, energy, interact and so forth. Certain excitations in materials can behave more like particles with all kinds of tunable properties, such as quasi-particles. Credit: Pixabay/CC0 Public domain
Quantum mechanics allows for the existence 'quasiparticles', excitations in materials which behave exactly like ordinary particle. Quasi-particles have the advantage over ordinary particles in that they can be engineered to change their properties. Erik van Heumen, an IoP physicist, describes recent experiments in which interactions between quasi-particles could be adjusted.

The mathematical branch of topology has been studying the shapes of things and the physical branch condensed matter Physics, which studies the behaviour of fluids and solids, have combined to create a new field of research: topological materials. The most exciting aspect of this new field is the discovery of exotic quasi-particles, which are local disturbances in materials that behave exactly as particles. It was already known that such quasi-particles exist from quantum descriptions of simple materials. Combining topology with quantum mechanics creates a new class of particles such as Dirac, Weyl fermions or magnetic monopoles.

Engineering interactions

Researchers can take control of the properties of quasi particles by making careful choices about the materials they use to create them. They are freed from the rigid rules that nature has set for ordinary particles. The desire to be able to tune the strength and type of interactions between quasi particles has been high up on the wish list.

A family of materials were discovered recently that have atoms in a so-called "kagome" lattice. Erik van Heumen's 'News & Views" article describes experiments that suggested the formation of a so called 'flux density wave' in these materials. This excitation provides confirmation of theoretical predictions that these materials might host exotically interacting quasi particles. This is a great opportunity for future research on topological materials.

Continue reading Emergent magnetic Monopoles Isolated Using Quantum-Annealing Computer

Further information: Kagome lattices containing chiral charges density, Nature Materials (2021). Information from Nature Materials Kagome Lattices with Chiral Charge Density, Journal (2021). DOI: 10.1038/s41563-021-01095-z

University of Amsterdam