Understanding Nonlinear Phononic Processes with Two- Dimensional Spectroscopy

Two-dimensional (2D) THz spectroscopy can reveal information about nonlinear energy transfer in solids. Experimental power dependent measurements can help determine the order of nonlinear mechanism. We used first-principles calculations to calculate anharmonic coupling constants for vibrational modes in beta-barium borate and compared with the recorded nonlinear 2D spectrum.