Spin-dependent Rabi oscillations in single quantum dots

Ultrafast optical pump of exciton resonance in single quantum dot by an elliptically polarized laser pulse is described by the integro-differential balance equations. Population and spin dynamics are investigated and spin-dependent Rabi oscillations are considered for the case of a flat quantum dot, with the lateral size greater than the height. The following peculiarities of temporal evolution have been found: (a) a beating of Rabi oscillations under an elliptically polarized pump and (b) quenching of spin orientation due to a spin-orbit splitting effect.

Figure 1

Resonant transitions between spin-degenerate ground and excited states, $\mid o,\pm 1⟩$ and $\mid e,\pm 1⟩$, under elliptically polarized excitation described by the polarization vectors, ${\mathbf{e}}_{\pm }$.

Figure 2

Temporal evolution of the total population, $n_t$, and the spin redistribution, $\delta n_t$, under the excitation amplitudes, $A=\pi$ (a) and $A=3.5\pi$ (b). Solid, dashed, and dotted curves correspond to $n_t$ under circular, elliptical, and linear polarized pumps, respectively. The dotted-dashed curve presents $\delta n_t$ under an elliptical polarized pump. The pulse profile is shown as the short-dot curve.

Figure 3

Quencing of the temporal response, both the total population $n_t$ (a–c) and the spin redistribution $\delta n_t$ (d), under resonant (solid curves) and nonresonant, with $\Delta \omega {\tau }_p=\pi ∕3$ (dashed curves) and $\Delta \omega {\tau }_p=2\pi ∕3$ (dotted curves), pumps. The excitation amplitudes, $A$, are indicated by arrows.

Figure 4

Oscillations of Rabi flopping population in $c$-band, $n$, and the spin redistribution, $\delta n$, versus excitation amplitude, $A$ (the same curves as in Fig. 1).