Hidden symmetries in the energy levels of excitonic ‘artificial atoms’

Abstract

Quantum dots or 'artificial atoms' are of fundamental and technological interest--for example, quantum dots may form the basis of new generations of lasers. The emission in quantum-dot lasers originates from the recombination of excitonic complexes, so it is important to understand the dot's internal electronic structure (and of fundamental interest to compare this to real atomic structure). Here we investigate artificial electronic structure by injecting optically a controlled number of electrons and holes into an isolated single quantum dot. The charge carriers form complexes that are artificial analogues of hydrogen, helium, lithium, beryllium, boron and carbon excitonic atoms. We observe that electrons and holes occupy the confined electronic shells in characteristic numbers according to the Pauli exclusion principle. In each degenerate shell, collective condensation of the electrons and holes into coherent many-exciton ground states takes place; this phenomenon results from hidden symmetries (the analogue of Hund's rules for real atoms) in the energy function that describes the multi-particle system. Breaking of the hidden symmetries leads to unusual quantum interferences in emission involving excited states.

Bright solid-state sources of indistinguishable single photons

“…When a laser pulse optically creates several electron-hole pairs in a QD, the system goes back to its ground state by emitting a cascade of photons. Thanks to the strong Coulomb interaction, only a single photon is emitted for a given emission energy 11 . This property has been exploited to generate single photons 6 , as well as single entangled photon pairs 12,13 .…”

Self-Assembled InGaAs Quantum Dot Clusters with Controlled Spatial and Spectral Properties

“…These states have been observed in previous studies performed on single InAs QDs grown by the SK method. 25,27 It has been suggested that these states arise from interaction between the band-filled wetting layer and the state-filled QD. 44 A precise analysis of the power dependence of PL intensity from the states other than s-shell states was complicated by the emergence of new peaks and the spectral broadening.…”

Spin-Dependent Coupling of Charged Quantum Dot Excitons with Continuum States

“…This model can be justified by the (395) shell structure observed when a quantum dot is filled either with excitons [1] or with electrons [2]. At low temperature, the artificial atom picture is strengthened by the long coherence times of an exciton in a quantum dot [3][4][5], motivating the application of quantum dots in quantum optics and quantum information processing.…”