Dark-bright excitons mixing in alloyed InGaAs self-assembled quantum dots

Abstract

Quantum dots are arguably one of the best platforms for optically accessible spin based qubits. The paramount demand of extended qubit storage time can be met by using quantum-dot-confined dark exciton: a longlived electron-hole pair with parallel spins. Despite its name the dark exciton reveals weak luminescence that can be directly measured. The origins of this optical activity remain largely unexplored. In this work, using the atomistic tight-binding method combined with configuration-interaction approach, we demonstrate that atomic-scale randomness strongly affects oscillator strength of dark excitons confined in self-assembled cylindrical InGaAs quantum dots with no need for faceting or shape-elongation. We show that this process is mediated by two mechanisms: mixing dark and bright configurations by exchange interaction, and equally important appearance of non-vanishing optical transition matrix elements that otherwise correspond to nominally forbidden transitions in a non-alloyed case. The alloy randomness has essential impact on both bright and dark exciton states, including their energy, emission intensity, and polarization angle. We conclude that, due to the atomic-scale alloy randomness, finding dots with desired dark exciton properties may require exploration of a large ensemble, similarly to how dots with low bright exciton splitting are selected for entanglement generation.

References in corpus (12)

• Coherent Population Trapping of an Electron Spin in a Single Negatively Charged Quantum Dot
• Importance of second-order piezoelectric effects in zincblende semiconductors
• Inversion of exciton level splitting in quantum dots
• Highly entangled photons from hybrid piezoelectric-semiconductor quantum dot devices
• Excitons, biexcitons and trions in self-assembled (In,Ga)As/GaAs quantum dots: Recombination energies, polarization and radiative lifetimes versus dot height
• Determinisitic Writing and Control of the Dark Exciton Spin using Short Single Optical Pulses
• Electronic structure of self-assembled InAs/InP quantum dots: A Comparison with self-assembled InAs/GaAs quantum dots
• Origin of non-linear piezoelectricity in III-V semiconductors: Internal strain and bond ionicity from hybrid-functional density functional theory
• Atomistic theory of dark excitons in self-assembled quantum dots of reduced symmetry
• In-plane radiative recombination channel of a dark exciton in self-assembled quantum dots
• Exciton lifetime and emission polarization dispersion in strongly in-plane asymmetric nanostructures
• Accessing the dark exciton spin in deterministic quantum-dot microlenses

Cited by in corpus (2)

• The optical Stark shift to control the dark exciton occupation of a quantum dot in a tilted magnetic field
• Eliminating the confined dark-exciton qubit precession using an externally applied magnetic field