Neutron scattering experiments on a honeycomb lattice magnet revealed a unique signature of quantum magnetism. These results showed how inelastic neutron scattering can be used to detect and decode quantum magnetism and distinguish truly quantum behavior from merely classical effects such as disorder.
In quantum magnets, magnetic moments fluctuate heavily and are strongly entangled with each other, a fundamental distinction from classical magnetism. An ongoing challenge is to measure and control the collective quantum properties of materials. By understanding the quantum magnetism of the honeycomb lattice material YbCl3 in terms of a canonical Heisenberg model, this work reveals a Van Hove singularity in the magnon spectrum, a clearly observable sharp feature within a continuum response. The demonstration of such a Van Hove singularity in a two-magnon continuum is important as a confirmation of broadly held notions of continua in quantum magnetism and additionally because analogous features in two-spinon continua could be used to distinguish quantum spin liquids from merely disordered systems. To unravel the properties of YbCl3, researchers used a combination of neutron scattering experiments at the Spallation Neutron Source and state-of-the-art modeling and theoretical calculations. This research demonstrates how neutron scattering can be used to identify the unique fingerprints of quantum magnetism.
