Correlated Spectra from Time-Linear Nonequilibrium GW Calculations

Time-resolved photoemission spectroscopy provides direct access to the nonequilibrium dynamics of electronic states. While nonequilibrium Green’s functions offer a rigorous framework to describe such spectra, their cubic scaling with the number of time steps severely limits their applicability to realistic materials. Approaches to reduce the numerical scaling, such as the HF-GKBA [1] or G1–G2 scheme [2], often compromise spectral information by neglecting correlation effects, effectively producing spectra at the mean-field level. Recently, a new method, the Real-Time Dyson Expansion (RT-DE) [3], was introduced to address these issues, achieving time-linear scaling while retaining dynamical correlations in the spectral function. So far, applications have been restricted to the second-order self-energy. Here, we present the first numerical results for the GW self-energy within the RT-DE framework.

[1] Lipavský et al., Phys. Rev. B 34, 6933 (1986)

[2] Schlünzen et al., Phys. Rev. Lett. 124, 076601 (2020)

[3] Reeves et al., Phys. Rev. Lett. 133, 226902 (2024)