Terahertz 2D coherent spectroscopy of transverse field quantum Ising model with further neighbor interactions

Recent advances in optical experimental methods in the terahertz range made terahertz 2D coherent spectroscopy (2DCS) possible. It has been a successful tool to probe interactions in various systems ranging from biexcitons in semiconductors to magnons in magnetic insulators. Here, we report results for the nonlinear 2DCS susceptibilities in the transverse field quantum Ising model including further neighbor interactions. Using a Jordan-Wigner transformation the model can be mapped to interacting fermions, for which we compute the 2DCS spectrum in a field-theoretical Keldysh approach. Information contained in the 2DCS can be used to identify interactions among the fermions, corresponding to next-nearest neighbor spin exchange couplings in the magnetic system.