Inverse Faraday Effect in Rashba two-dimensional electron systems: interplay of spin and orbital effects

Abstract

The inverse Faraday effect (IFE) refers to the generation of a DC magnetization by circularly polarized light through the transfer of optical angular momentum to electronic degrees of freedom. In conducting systems, this response can arise from two microscopic channels - spin polarization of itinerant electrons and orbital magnetization generated by circulating charge currents. However, the orbital contribution to the inverse Faraday effect in spin-orbit-coupled conducting systems remains largely unexplored. We present a theoretical analysis of the IFE in disordered two-dimensional electron systems with Rashba spin-orbit coupling using both the quantum kinetic equation and Green's-function diagrammatics. We find that in a noninteracting Rashba metal the orbital magnetization is strongly modified by spin-orbit coupling and can become comparable to, or exceed, the spin magnetization for realistic parameter regimes. When the radiation frequency approaches the Rashba spin splitting, both spin and orbital magnetizations exhibit resonant enhancement. These results clarify the microscopic origin of light-induced magnetization and highlight the interplay of spin and orbital mechanisms in optically driven magnetization dynamics in low-dimensional electronic systems.

Figures (7)

• Figure 1: The diagrams responsible for spin IFE.
• Figure 2: Plot of orbital IFE magnetization in terms of dimensionless $\mathcal{F}\left(\frac{\omega}{\varepsilon_F},\varepsilon_F\tau\right)$ vs light frequency normalized by the Fermi energy, $\omega/\varepsilon_F$ for different values of $\varepsilon_F\tau$ in the normal 2DEG without SOC.
• Figure 3: Plot of dimensionless spin IFE magnetization $\mathbf{M}_{\text{spin}}$ vs light frequency normalized by the Fermi energy, $\omega/\varepsilon_F$ for different values of $\varepsilon_F\tau$ in 2DEG with Rashba SOC for $\alpha_{so}k_F/\varepsilon_F=0.1$.
• Figure 4: Plot of dimensionless total orbital IFE magnetization $\mathbf{M_{orb}^{total}}-\mathbf{M_{orb}^{normal}}$ vs light frequency normalized by the Fermi energy, $\omega/\varepsilon_F$ for different values of $\varepsilon_F\tau$ in 2DEG with Rashba SOC for $\alpha_{so}k_F/\varepsilon_F=0.1$.
• Figure 5: Plot of dimensionless bare orbital IFE magnetization $\mathbf{M_{orb}^{bare}}-\mathbf{M_{orb}^{normal}}$ vs light frequency normalized by the Fermi energy, $\omega/\varepsilon_F$ for different values of $\varepsilon_F\tau$ in 2DEG with Rashba SOC for $\alpha_{so}k_F/\varepsilon_F=0.1$.