  We theoretically study the inverse Faraday effect (IFE), i.e., photo-induced
magnetization, in two-dimensional Rashba spin-orbit coupled electron systems
irradiated by a circularly polarized light. The quantum master
(Gorini-Kossakowski-Sudarshan-Lindblad) equation enables us to accurately
compute the laser driven dynamics, taking inevitable dissipation effects into
account. To find the universal features of laser-driven magnetization and its
dynamics, we comprehensively investigate (i) the nonequilibrium steady state
(NESS) driven by a continuous wave and (ii) ultrafast spin dynamics driven by
short laser pulses. In the NESS (i), the laser-induced magnetization and its
dependence of several parameters (laser frequency, laser field strength,
temperature, dissipation strength, etc.) are shown to be in good agreement with
the predictions from Floquet theory for dissipative systems in the
high-frequency regime. In the case (ii), we focus on ferromagnetic metal states
by introducing an effective magnetic field to the Rashba model as the mean
field of electron-electron interaction. We find that a precession of the
magnetic moment occurs due to the pulse-driven instantaneous magnetic field and
the initial phase of the precession is controlled by changing the sign of light
polarization. This is well consistent with the spin dynamics observed in
experiments of laser-pulse-driven IFE. We discuss how the pulse-driven dynamics
are captured by the Floquet theory. Our results %pave the way for computing
provides a microscopic method to compute ultrafast dynamics in many electron
systems irradiated by intense light.
