Two-dimensional spectroscopy of exactly solvable spin liquids

Over the last few years, advances in generating coherent terahertz pulses enabled probing quantum many-body phenomena using higher dimensional spectroscopy, revealing unique features of excitations in correlated materials such as superconductors or quantum magnets. The technique consists of measuring nonlinear response functions after a train of pulses is irradiated to the sample. In this talk, we present theoretical results on two-dimensional spectroscopy of exactly solvable spin liquids, showing how the Z2 gauge fields and Majorana matter fermions can be disentangled. For concreteness, we consider the Kitaev model on the honeycomb and square octagon lattices. While both models are exactly solvable, we highlight how the lattice geometry affects the non-vanishing components. We show how distinct spin liquid fingerprints can appear in the higher-order susceptibilities when using crossed-light polarizations, focusing on the effects of localized matter fermions around Z2 fluxes. Our results show that the diagonal and non-diagonal components of the susceptibility tensor have very different properties due to distinct interference processes. Finally, we compare our findings to other exactly solvable spin liquid models.