Title: 2D Spectroscopy for 1D Spin Chains with Fractionalized Excitations
Abstract: The conventional 1D optical spectroscopy uses one handle which is the frequency of the probing electromagnetic waves. This results in a 1D spectrum of the response as a function of the probing frequency. One can significantly extend the utility of the optical spectroscopy by adding more handles, or more electromagnetic wave. The outcome is known as 2D coherent spectroscopy. Since the 2D coherent spectroscopy has more handles, one naturally expects that this technique can obtain more information about the material that is being investigated.
Recently, interesting works appear which propose that CoNb2O6, long believed transverse field Ising model (TFIM) for 30 years [1], is in fact well described by the twisted Kitaev model (TKM) with bond dependent interaction [2,3]. The difficulty of identifying a proper model with 1D spectroscopy originates from the fact that elementary excitations of both models are spinons. We consider 2D spectroscopy as a tool for distinguishing between two magnetic models, the TFIM and TKM. Unlike 1D spectroscopy result (dynamical spin structure factor shown in Fig.1 (a,b)), the 2D spectrum (3rd order magnetic susceptibility shown in Fig.1 (c,d)) show clear differences which originate from the interplay between spinons.