Anomalous Stark Shifts in Single Vertically Coupled Pairs of InGaAs Quantum Dots

TL;DR

This paper investigates how electric fields influence the Stark shifts in single pairs of vertically coupled InGaAs quantum dots, revealing strong tunnelling interactions and wavefunction redistributions that affect exciton properties.

Contribution

It provides new insights into the Stark shift behaviour and tunnelling effects in coupled quantum dots under varying electric fields.

Findings

Pronounced changes in Stark shift behaviour due to wavefunction redistribution.

Identification of coherent tunnelling between QD ground states at low fields.

Distortion of Stark shift indicating tunnelling between ground and excited states at higher fields.

Abstract

Vertically coupled Stranski Krastanow QDs are predicted to exhibit strong tunnelling interactions that lead to the formation of hybridised states. We report the results of investigations into single pairs of coupled QDs in the presence of an electric field that is able to bring individual carrier levels into resonance and to investigate the Stark shift properties of the excitons present. Pronounced changes in the Stark shift behaviour of exciton features are identified and attributed to the significant redistribution of the carrier wavefunctions as resonance between two QDs is achieved. At low electric fields coherent tunnelling between the two QD ground states is identified from the change in sign of the permanent dipole moment and dramatic increase of the electron polarisability, and at higher electric fields a distortion of the Stark shift is attributed to a coherent tunnelling effect between the ground state of the upper QD and the excited state of the lower QD.