ABSTRACT The physical origin of the ultrashort dephasing time T 2 (≈ O(1) fs), persistently addressed in the solid‐state high‐harmonic generation (HHG), remains an unresolved and challenging issue because the electron scattering at such a short timescale within solids is hardly identified. Here we investigate HHG of the 1D Hubbard model in the dissipative quantum environment within a frame of the Lindblad equation. In the study, in the limit of a small interatomic distance, we make the first verification of the solid‐state Dicke superradiance, the coherent stimulated emission triggered by the spontaneous emission, as well as the broadband emission mimicking the blackbody radiation due to the electron scattering in each harmonic multiple. Further, we find a strong destructive interference between the Dicke superradiance and the broadband emission, which makes a scale down of the effective electron scattering time and leads to just few‐femtosecond dephasing time T 2 . This finding explains a long‐standing problem of the ultrafast femtosecond electron dephasing in HHG. The present study could also serve as a pertinent platform for understanding the nonequilibrium dissipative dynamics of correlated electron systems.
By numerically calculating the time-evolved Wigner functions, we investigate the dynamics of a few-photon superposed (e.g., up to two ones) state in a dissipating cavity. It is shown that, the negativity of the Wigner function of the photonic state unquestionably vanishes with the cavity's dissipation. As a consequence, the nonclassical effects related to the negativity of the Wigner function should be weakened gradually. However, it is found that the value of the second-order correlation function
g(2)(0) (which serves usually as the standard criterion of a typical nonclassical effect, i.e.,
g(2)(0)<1 implies that the photon is anti-bunching) is a dynamical invariant during the dissipative process of the cavity. This feature is also proven analytically and suggests that
g(2)(0) might not be a good physical parameter to describe the photonic decays. Alternatively, we find that the anti-normal-order correlation function
g(2A)(0) changes with the cavity's dissipation and thus is more suitable to describe the dissipative-dependent cavity. Finally, we propose an experimental approach to test the above arguments with a practically-existing cavity QED system.
Time-resolved photoemission spectroscopy provides a unique and direct way to explore the real-time nonequilibrium dynamics of electrons and holes. The formal theory of the spectral function evolution requires inclusion of electronic correlations and dissipation, which are challenging due to the associated long simulation timescales which translate to a high computational cost. Recent methodological developments, namely the Real-Time Dyson Expansion, as well as theoretical developments of many-body perturbation theory for dissipative systems, have allowed for the study of driven-dissipative interacting quantum systems. In this work, we implement the hitherto unrealized study of driven-dissipative interacting quantum systems which includes driven dynamical correlations and utilizes these new methods and perturbative expansions. We illustrate the combined formalism on a prototypical two-band semiconductor model with long-range density-density Coulomb interactions. We show that the intraband thermalization of conduction band electrons induces nontrivial time-dependent changes in the system's bandstructure and a time-evolving band-gap renormalization (with a reduction by up to 10\%). We show that the qualitative features are preserved for a variety of parameters, discuss the corresponding spectral dynamics, and provide an outlook on the newly introduced simulation framework, which enables treating electron-electron scattering and dissipation effects on equal footing.