Strong Electron-Hole Exchange in Coherently Coupled Quantum Dots

TL;DR

This paper explores the dominant electron-hole exchange interactions in vertically stacked quantum dots with weak tunneling, revealing new regimes of spin coupling and enabling all-optical charge sensing through differential transmission.

Contribution

It introduces a regime where electron-hole exchange dominates in coupled quantum dots and demonstrates all-optical charge sensing enabled by small tunnel coupling.

Findings

Electron-hole exchange is the dominant spin interaction in the studied regime.

Tuning gate bias can switch off the coupling, revealing different spin regimes.

All-optical charge sensing is demonstrated via conditional exciton energy shifts.

Abstract

We have investigated few-body states in vertically stacked quantum dots. Due to small inter-dot tunneling rate, the coupling in our system is in a previously unexplored regime where electron-hole exchange is the dominant spin interaction. By tuning the gate bias, we are able to turn this coupling off and study a complementary regime where total electron spin is a good quantum number. The use of differential transmission allows us to obtain unambiguous signatures of the interplay between electron and hole spin interactions. Small tunnel coupling also enables us to demonstrate all-optical charge sensing, where conditional exciton energy shift in one dot identifies the charging state of the coupled partner.