# Optimal electro-mechanical control of the excitonic fine structures of droplet epitaxial quantum dots

## TL;DR

This paper presents a theoretical and computational study on how electro-mechanical control using micro-machined piezoelectric actuators can eliminate the excitonic fine structure splitting in droplet epitaxial quantum dots, enabling entangled photon emission.

## Contribution

It reveals the principles for designing actuators to suppress FSS in quantum dots and shows that a single symmetric bi-axial stress can achieve full FSS elimination.

## Key findings

- Two independent stresses can suppress FSS.
- Single symmetric bi-axial stress can eliminate FSS.
- Design principles for optimal actuator configuration.

## Abstract

The intrinsic fine structure splittings (FSSs) of the exciton states of semiconductor quantum dots (QDs) are known to be the major obstacle for realizing the QD-based entangled photon pair emitters. In this study, we present a theoretical and computational investigation of the excitonic fine structures of droplet-epitaxial (DE) GaAs/AlGaAs QDs under the electro-mechanical control of micro-machined piezoelectricity actuators. From the group theory analysis with numerical confirmation based on the developed exciton theory, we reveal the general principle for the optimal design of micro-machined actuators whose application on to an elongated QD can certainly suppress its FSS. We show that the use of two independently tuning stresses is sufficient to achieve the FSS-elimination but is not always necessary as widely deemed. The use of a single tuning stress to eliminate the FSS of an elongated QD is possible as long as the crystal structure of the actuator material is in coincidence with that of the QD. As a feasible example, we show that a {\it single} symmetric bi-axial stress naturally generated from the $(001)$ PMN-PT actuator can be used as a single tuning knob to make the full FSS-elimination for elongated DE GaAs QDs.