A quantum spin liquid is a disordered but highly entangled magnetic state with fractional spin excitations. The exactly solvable Kitaev model for the ground state of a honeycomb lattice is its best example. Under a magnetic field, a spin flip fractionalizes into two anyons, quasiparticles with more complex exchange statistics than fermions or bosons: a pair of gauge fluxes and a Majorana fermion. This fractionalization was observed by nuclear magnetic resonance in α-RuCl₃. It survives in a broad range of temperatures and magnetic fields, which establishes the honeycomb magnet α-RuCl₃ as a unique platform for future investigations of anyons.

α-RuCl₃ crystals were grown by Daniel Biner in the group of PD Dr. Karl Krämer at the DCB. Magnetic properties were measured in the group of Christian Rüegg at PSI. Solid state NMR investigations were done in the group of Martin Klanjšek at the Jožef Stefan Institute, Ljubljana, Slovenia.

References:

• N. Janša, A. Zorko, M. Gomilšek, M. Pregelj, K. W. Krämer, D. Biner, A. Biffin, Ch. Rüegg, M. Klanjšek;
  "Observation of two types of fractional excitation in the Kitaev honeycomb magnet"
  Nature Physics, 2018, 14(8), 786-790; doi:10.1038/s41567-018-0129-5.