Coherent Modulation of Quasiparticle Scattering Rates in a Photoexcited Charge-Density-Wave System

We present a complementary experimental and theoretical investigation of relaxation dynamics in the charge-density-wave (CDW) system TbTe₃ after ultrafast optical excitation. While the CDW is excited and the corresponding order parameter exhibits typical oscillations, the relaxation rates of excited photocarriers show an unusual transient modulation. Using state-of-the-art time-dependent Green’s functions simulations we can capture the relaxation dynamics and trace their microscopic origin. From a detailed analysis of the electron self-energy we identify the transient modulation of the relaxation to be due to modulations of the electron-electron scattering phase space driven by the photoinduced collective CDW excitation. Our synergistic experimental-theoretical approach is general and can deliver new microscopic information from excitation of coherent oscillations and tracking the relaxation dynamics.