Dynamic response of artificial bipolar molecules

TL;DR

This paper investigates the equilibrium and dynamic properties of coupled quantum dots containing particles of opposite charge, revealing mode coupling, anticrossing phenomena, and effects of symmetry breaking on excitations.

Contribution

It provides a detailed analysis of magnetoplasma excitations in bipolar quantum dot molecules, highlighting mode interactions and the impact of symmetry breaking on excitation spectra.

Findings

Strong coupling between center-of-mass derived modes causes anticrossing.

Oscillator strength transfer from acoustic to optical modes observed.

Breaking of Kohn theorem leads to excitation of additional modes.

Abstract

We calculate the equilibrium properties and the dynamic response of two vertically coupled circular quantum dots populated by particles of different electrical charge sign, i.e. electrons and holes. The equilibrium density profiles are obtained and used to compute the frequencies and oscillator strengths of magnetoplasma excitations. We find a strong coupling between the modes derived from the center-of-mass modes of the individual dots which leads to an anticrossing with a pronounced oscillator strength transfer from the ``acoustic'' to the ``optical'' branch. Also, due to breaking of the generalized Kohn theorem a number of other than center-of-mass modes are excited whose oscillator strengths, however, are rather weak.