Experimental Measurement of Ru³⁺Form Factor

The need for fault tolerant quantum computation has resulted in a large push for materials realizing Kitaev’s model of bond dependent exchange on a honeycomb lattice. In this regard, α-RuCl₃ remains one of the most promising candidate materials. A host of neutron scattering, thermal Hall, Raman, and THz spectroscopy experiments have shown evidence that α-RuCl₃ is proximate to a Kitaev quantum spin liquid (QSL), with the QSL state stabilized through application of a magnetic field within the honeycomb plane. Despite the large amount of interest, several unanswered questions remain, including the true form of the low energy Hamiltonian of the system. Quantitative analysis of neutron scattering data would be aided by an accurate determination of the magnetic form factor of Ru³⁺, where the mixed spin-orbital doublet ground state is expected to show notable deviations from the spherical approximation. In this talk, I will discuss recent experimental results where we have directly measured the magnetic form factor through half-polarized neutron diffraction of α-RuCl₃ under an applied magnetic field above T_N , well into the paramagnetic regime.