Dr. Ludovic Jaubert (University of Bordeaux)
"When neutrons see half moons"
We study the formation of magnetic clusters in frustrated magnets in their cooperative paramagnetic regime. For this purpose, we
consider the J1-J2-J3 models on kagome and pyrochlore lattices, with J2 = J3 = J and either Ising or classical Heisenberg spins.
In the absence of further-neighbor couplings, J = 0, the system is in the Coulomb phase with magnetic correlations well
characterized by pinch-point singularities. Further-neighbor couplings lead to the formation of magnetic clusters. With Ising spins,
these clusters are made of topological charges bearing the same gauge charge. Upon increasing J, the static and dynamical magnetic
structure factors as measured by neutron scattering develop half-moon patterns. These characteristic patterns are a dispersive
complement of the pinch-point singularities when the flat bands get excited, and signal the proximity to a Coulomb phase.
-- Udagawa, Jaubert, Castelnovo & Moessner, PRB 94, 104416 (2016)
-- Mizoguchi, Jaubert & Udagawa, PRL 119, 077207 (2017)
-- Mizoguchi, Jaubert, Moessner & Udagawa, PRB 98, 144446 (2018)