Emission spectrum of quasiresonant laterally coupled quantum dots

We calculate the emission spectrum of neutral and charged excitons in a pair of laterally coupled InGaAs quantum dots with nearly degenerate energy levels. As the interdot distance decreases, a number of changes take place in the emission spectrum which can be used as indications of molecular coupling. These signatures ensue from the stronger tunnel coupling of trions as compared to that of neutral excitons.

Figure 1

Contour plot of the confinement potential for slightly asymmetric, laterally coupled QDs with an interdot distance $d=40$ nm.

Figure 2

Emission spectrum of negative trions (solid red lines) and neutral excitons (dashed green lines) for different interdot distances. Grey lines are a guide to the eyes. See text for the meaning of labels.

Figure 3

Energy of the lowest exciton states as a function of the interdot distance. The insets show the charge density of the electron (red or dark gray line) and hole (green or light gray line) within the exciton complex for the optically active states at $d=40$ nm (right) and $d=20$ nm (left).

Figure 4

Energy of the lowest negative trion states (a) and electron states (b) as a function of the interdot distance. The lateral insets show the charge density of the electron (red or dark gray line) and hole (green or light gray line) at $d=40$ nm (right) and $d=20$ nm (left). Vertical arrows indicate the transitions observed in Fig. 2.

Figure 5

Emission spectrum of positive trions for different interdot distances. Dashed lines are a guide to the eyes.

Figure 6

Energy of the lowest positive trion states (a) and hole states (b) as a function of the interdot distance. The lateral insets show the charge density of the electron (red or dark gray line) and the hole (green or light gray line) at $d=40$ nm (right) and $d=20$ nm (left). Vertical arrows indicate the transitions observed in 5.

Figure 7

Emission spectrum of negative trions (solid red lines), neutral excitons (dashed green line), and positive trions (dotted blue lines) for different interdot distances.