Quasiparticles Team Up
Materials exhibiting the so-called fractional quantum Hall effect host quasiparticles that are neither fermions nor bosons. The electric charges of these entities, known as anyons, have specific fractional values. But dedicated experiments have unexpectedly measured charges that are multiples of those values. Now a theoretical study by Mytraya Gattu and Jainendra Jain at Pennsylvania State University has shown that these observations are caused by the anyons binding together to form “molecules” [1]. This finding is surprising because anyons in a given fractional quantum Hall state all have the same charge and were thus assumed to repel each other.
Using a powerful mathematical framework called composite fermion theory, Gattu and Jain calculated the energies of anyons in various settings. The researchers compared the energy of a group of anyons with the energy of the same anyons when separated. This comparison enabled them to determine whether adding an anyon to the group lowers the total energy, a result that signals molecule formation.
Gattu and Jain found that anyons in fractional quantum Hall states often exist as molecules. The properties of these molecules, such as their number of anyons and their size, depend greatly on the nature of the state and on the details of the electron interactions. The researchers also used their calculations to make several predictions that could be tested in future experiments. In particular, they hypothesize that some charge-1/4 “non-Abelian” anyons can pair up to form charge-1/2 “Abelian” anyons. This process could affect the behavior of topological quantum computers because these devices—which exist only in speculative proposals—rely specifically on non-Abelian anyons.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- M. Gattu and J. K. Jain, “Molecular anyons in the fractional quantum Hall effect,” Phys. Rev. Lett. 135, 236601 (2025).