Quantum ring with the Rashba spin-orbit interaction in the regime of strong light-matter coupling

We developed the theory of electronic properties of semiconductor quantum rings with the Rashba spin-orbit interaction irradiated by an off-resonant high-frequency electromagnetic field (dressing field). Within the Floquet theory of periodically driven quantum systems, it is demonstrated that the dressing field drastically modifies all electronic characteristics of the rings, including spin-orbit coupling, effective electron mass, and optical response. In particular, the present effect paves the way to controlling the spin polarization of electrons with light in prospective ring-shaped spintronic devices.

Figure 1

Sketch of the system under consideration: The quantum ring (QR) with the radius $R$ irradiated by a linearly polarized electromagnetic (EM) wave with the electric-field amplitude $E_0$. The electron spin (the dark blue arrow) is directed along the local quantization axis (the dashed blue line) with the spin angle $\xi$.

Figure 2

Electronic characteristics of InGaAs-based QR (the electron effective mass is $m=0.045m_0$, the Rashba coupling constant is $\alpha ={10}^4$ m/s, and the QR radius is $R=200$ nm) irradiated by a dressing field with the frequency $\omega =1.6\times {10}^{12}\text{rad}/\text{s}$: (a) Dependence of the spin angle, $\xi$, on the irradiation intensity, $I$; (b) dependence of the first nine electron energy levels, ${\varepsilon }_{\lambda n}^s$, on the irradiation intensity, $I$, for the counterclockwise electron rotation in the ring ($\lambda =+$), where the dashed and solid lines correspond to different spin orientations ($s=\pm 1$).

Figure 3

Absorption spectra of the probe field with the frequency $\mathrm{\Omega }$ for the InGaAs-based QR (the electron effective mass is $m=0.045m_0$, the Rashba coupling constant is $\alpha ={10}^4$ m/s, the electron relaxation time is $\tau =70$ ps, the temperature is $T=5$ K, the Fermi energy is $\mu =1$ meV, and the QR radius is $R=200$ nm) irradiated by a dressing field with the frequency $\omega =1.6\times {10}^{12}\text{rad}/\text{s}$ and different irradiation intensities, $I$.