Dynamic localization in finite quantum-dot superlattices: A pure ac field effect

We propose that dynamic localization can be unambiguously observed through the linear optical absorption coefficient of a finite quantum dot superlattice. It is shown that the miniband collapse is almost exact in a pure ac field driven system. In the presence of Coulomb interaction, the dynamic localization is partially preserved, showing clear fingerprints in the modulation of the excitonic spectra. The spectra are obtained within an extended semiconductor Bloch equation framework, taking into account the center-of-mass motion for a finite system.

Figure 1

Quantum rod $3.5\mu \mathrm{m}$ long of InP and a superlattice of 20 ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}$ dots (InP barriers) in its central part.

Figure 2

(Color online) Optical absorption without Coulomb interaction. Solid line for free ac field; short dashed line for $ed{F}_0∕\hslash \Omega =x=0.5$; dot-dashed line for $x=1.0$; dotted line for $x=2.4$, and two dots-dashed line for $x=3.5$. The inset on the right shows the miniband width obtained from the optical absorption spectra (full circle) and from the formula (solid line) $\Delta E=J_0\left(x\right)\Delta E_0$, where $\Delta E_0$ is the miniband width for field-free and without Coulomb interaction. In the inset on the left we show the spectrum for the case with $x=2.4$ (dotted line) and the spectrum for a single dot, without Coulomb interaction and ac field (solid line).

Figure 3

(Color online) Optical absorption considering the Coulomb interaction. Solid line for free terahertz fields; short dashed line for $x=ed{F}_0∕\hslash \Omega =1.5$; dotted line for $x=2.4$; long dashed line for $x=3.5$, and dot-dashed line for $x=5.52$. The inset on the right shows the dynamical localization coefficient defined by $\eta =(\Delta E-\Delta E_{1d})∕\Delta E_{1d}$, where $\Delta E$ is width of the excitonic spectrum (full width at half maximum) and $\Delta E_{1d}$ the excitonic linewidth of a single dot for ac field free (inset on the left).