Optoelectronic control of spin dynamics at near-terahertz frequencies in magnetically doped quantum wells

We use time-resolved Kerr rotation to demonstrate optical and electronic tuning of both electronic and local moment (Mn²⁺) spin dynamics in electrically gated parabolic quantum wells derived from II-VI diluted magnetic semiconductors. By changing either the electrical bias or laser energy, the electron spin precession frequency is varied from 0.1 to 0.8 THz at a magnetic field of 3 T and at a temperature of 5 K. The corresponding range of electrically tuned effective electron g-factor is an order of magnitude larger compared with similar nonmagnetic III-V parabolic quantum wells. Additionally, we demonstrate that such structures allow electrical modulation of local moment dynamics in the solid state, which is manifested as changes in amplitude and lifetime of Mn²⁺ spin precession under electrical bias. The large variation of electron and Mn-ion spin dynamics is explained by changes in magnitude of the sp-d exchange overlap.