Nonequilibrium Dynamics in a Quantum Spin Chain with Pump-Probe Resonant Inelastic X-ray Scattering

Abstract: We investigate the nonequilibrium dynamics of the transverse field Ising chain (TFIC) using time-resolved resonant inelastic X-ray scattering (tr-RIXS) in a pump-probe setup within a condensed matter setting. The tr-RIXS spectra reveal distinctive features, including two-kink continua at high energies and oscillatory spectral weight at low energies, both strongly influenced by the pump dynamics. By systematically analyzing the nonequilibrium tr-RIXS cross section under various pump configurations, we demonstrate how the spectra encode detailed information about the system's transient states, capturing instantaneous Hamiltonian parameters and the traversal of equilibrium quantum critical points during dynamic evolution. Notably, we uncover a one-to-one correspondence between oscillatory features in the low-energy spectra and dynamical quantum phase transitions, offering a novel and experimentally accessible approach for their detection. These findings highlight the versatility of tr-RIXS as a powerful tool for studying quantum systems far from equilibrium and their critical phenomena.