Theory of excitons, charged excitons, exciton fine-structure and entangled excitons in self-assembled semiconductor quantum dots (original) (raw)
Theory of Excitons in InGaAs/GaAs Quantum Dots
NanoScience and Technology, 2008
We employ the configuration interaction (CI) method in order to discuss many-particle properties of quantum dots as functions of the dots' size, shape and composition. Single-particle states, necessary for the CI-basis expansion, are calculated by eight-band k•p theory. Special emphasis is put on the role of strain and piezoelectricity, where the latter is treated up to second order. Finally, we address the inverse problem of fitting spectroscopic data to our detailed theoretical model leading to the determination of size, shape and composition as adjustable parameters.
Charged Excitons in Self-Assembled Semiconductor Quantum Dots
Physical Review Letters, 1997
Interband excitations of an ensemble of InAs self-assembled quantum dots have been directly observed in transmission experiments. The dots are embedded in a field-effect structure allowing us to load the dots electrically. We establish an exact correspondence between Coulomb blockade in the device's vertical transport properties and Pauli blocking in the transmission spectra. We observe substantial shifts, up to 20 meV, in the energies of the higher excitations on occupation of the electron ground state. We argue that this is a consequence of an exciton-electron interaction. [S0031-9007(97)04868-0]
Entangled exciton states in quantum dot molecules
Physica E-low-dimensional Systems & Nanostructures, 2002
The exciton states in self-assembled InAs/GaAs quantum dot molecules have been studied by optical spectroscopy and the results have been compared to detailed theoretical calculations. We demonstrate that excitons in symmetric molecule structures form entangled quantum states with the degree of entanglement controlled by tunneling and Coulomb interaction.
Multiexciton complexes in InAs self-assembled quantum dots
Journal of Applied Physics, 2009
We review our recent work on multiexciton complexes in InAs self-assembled quantum dots using a combination of effective mass, k · p, and atomistic sp 3 s ء d 5 tight-binding approaches. The single-particle levels from effective mass, k · p, and atomistic tight-binding models are used as input into configuration-interaction calculation of multiexciton spectra. We describe the principles of the atomistic approach and apply all these computational tools to illustrate the concept of hidden symmetry as underlying principle in energy levels of multiexciton complexes, optical detection of electron spin polarization, tunneling of holes in quantum dot molecules, and tuning of multiexciton spectra with lateral electric fields for entangled photon pair generation.
Entangled states of electron–hole complex in a single InAs/GaAs coupled quantum dot molecule
Physica E: Low-dimensional Systems and Nanostructures, 2002
We summarize here results of calculations and experiments on electron and valence hole states in a single pair of vertically stacked and electronically coupled InAs self-assembled quantum dots. In perfectly aligned quantum dots one can relate an electron-hole complex to a pair of entangled qubits. The information carried by individual qubit is related to the quantum dot index (isospin) of individual carrier. The quality of fabricated quantum dot molecules is identiÿed from the exciton ÿne structure in a magnetic ÿeld. ?
Physical Review B, 2012
We investigate the vertical electric field tuning of the exciton fine structure splitting (FSS) in several InGaAs and GaAs quantum dots (QDs) using the atomistic empirical pseudopotential approach and configuration interaction. We find that the FSS is surprisingly tunable, with a rate similar to the one reported for lateral electric fields. The minimum FSS for GaAs QDs often lies below the radiative linewidth, which makes them good candidates for the generation of entangled photon pairs. We highlight, however, that random alloy fluctuations affect the minimum FSS by ± 1.4 µeV, so that a post-selection of QDs may still be beneficial to obtain entangled photon pairs with the highest fidelity. We suggest a simple experimental procedure for this task. The FSS is therefore a rare observable, where the specific decoration of the random alloy lattice, significantly matters.
Fine Structure of Excitons inInAs/GaAsCoupled Quantum Dots: A Sensitive Test of Electronic Coupling
Physical Review Letters, 2003
Exciton fine structure in InAs=GaAs coupled quantum dots has been studied by photoluminescence spectroscopy in magnetic fields up to 8 T. Pronounced anticrossings and mixings of optically bright and dark states as functions of magnetic field are seen. A theoretical treatment of the mixing of the excitonic states has been developed, and it traces observed features to structural asymmetries. These results provide direct evidence for coherent coupling of excitons in quantum dot molecules.
2018
LARGE-SCALE SEMI-EMPIRICAL PSEUDOPOTENTIAL ELECTRONIC STRUCTURE OF SELF-ASSEMBLED INGAAS QUANTUM DOTS Mustafa Kahraman M.S. in Department of Physics Advisor: Ceyhun Bulutay August 2018 The so-called second quantum revolution emerged at the beginning of the second millennium, opening up a path to realization of spin-qubit-based quantum computing by means of controlling and protecting quantum coherent processes. Thus, along this spirit, the self-assembled quantum dots (SAQD) made a transition from conventional optoelectronic devices to spin-qubit applications. One specific problem that can benefit from this is the electron spin resonance (ESR) of a single-electron in a SAQD which could not be reproduced after its demonstration for more than ten years. The lack of insight for the electronic structure of SAQDs and g-factors changing with its properties might be the underlying reason for the decade-old puzzle. Towards the goal of understanding the ESR, atomistic large-scale semi-empirica...
Excitonic energy shell structure of self-assembled InGaAs/GaAs quantum dots
Physical review letters, 2004
Performing optical spectroscopy of highly homogeneous quantum dot arrays in ultrahigh magnetic fields, an unprecedently well resolved Fock-Darwin spectrum is observed. The existence of up to four degenerate electronic shells is demonstrated where the magnetic field lifts the initial degeneracies, which reappear when levels with different angular momenta come into resonance. The resulting level shifting and crossing pattern also show evidence of many-body effects such as the mixing of configurations and exciton condensation at the resonances.