Electronic correlation and quantum memory effects in the ultrafast laser induced charge and spin dynamics in bulk Ni

We analyze the roles of electronic correlations and memory effects in the ultrafast charge and spin dynamics in bulk ferromagnetic Ni excited by laser pulses. The studies are performed by using the Time-Dependent Density-Functional Theory+Dynamical Mean-Field Theory (TDDFT+DMFT) approach [1;2], where the effects of strong correlations are taken into account by means of the exchange-correlation (XC) kernel obtained from the DMFT local-in-space charge susceptibility. It is shown that the TDDFT+DMFT results for the time-dependent ultrafast demagnetization in Ni is much closer to the experimental data as compared to the ones obtained with TDLDA that strongly underestimates the change of the magnetization. We argue that the main reason for a good agreement between the TDDFT+DMFT and experimental data is due to inclusion of the memory effects through the frequency-dependent DMFT XC kernel.
[1] V. Turkowski, T.S. Rahman, Journal of Physics: Condensed Matter 29 (2017) 455601.
[2] S.R. Acharya, V. Turkowski, T.S. Rahman, Computation 4 (2016) 34.