Disentangling spin excitation continua in classical and quantum magnets using two-dimensional nonlinear spectroscopy

Two-dimensional coherent spectroscopy ($2D\phantom{\rule{0}{0ex}}C\phantom{\rule{0}{0ex}}S$) has emerged as a powerful tool for probing nonlinear excitation dynamics in quantum magnets, overcoming the limitations of traditional inelastic neutron scattering as a linear probe. The authors use here classical molecular dynamics simulations to compare the $2D\phantom{\rule{0}{0ex}}C\phantom{\rule{0}{0ex}}S$ responses of various models with large Kitaev interactions, revealing distinct features between quantum spin liquids, classical spin liquids, and large unit cell magnetic orders. These findings underscore the potential for $2D\phantom{\rule{0}{0ex}}C\phantom{\rule{0}{0ex}}S$ in disentangling the complex dynamics of frustrated magnetic systems.