Probing the dark exciton states of a single quantum dot using photocurrent spectroscopy in magnetic fields

TL;DR

This study uses high-resolution photoluminescence and photocurrent spectroscopy to investigate dark and bright exciton states in a single quantum dot under magnetic fields, revealing Zeeman splitting and state mixing.

Contribution

It demonstrates a method to probe dark exciton states in a single quantum dot using photocurrent spectroscopy combined with magnetic field application.

Findings

Observation of Zeeman splitting in PL and PC spectra

Detection of dark exciton states in Voigt geometry

Confirmation of state mixing via polarization-resolved spectra

Abstract

We report on high-resolution photoluminescence (PL) and photocurrent (PC) spectroscopies of a single self-assembled InAs/GaAs quantum dot (QD) embedded in an n-i-Schottky device with an applied magnetic field in Faraday and Voigt geometries. The single-QD PC spectrum of neutral exciton (X$^0$) is obtained by sweeping the bias-dependent X$^0$ transition energy to achieve resonance with a fixed narrow-bandwidth laser through quantum-confined Stark effect. With a magnetic field applied in Faraday geometry, the diamagnetic effect and the Zeeman splitting of X$^0$ are observed both in PL and PC spectra. When the magnetic field is applied in Voigt geometry, the mixture of bright and dark states results in an observation of dark exciton states, which are confirmed by the polarization-resolved PL and PC spectra.