We report a comprehensive discussion of quantum interference effects due to the finite structure of excitons in quantum rings and their first experimental corroboration observed in the optical recombinations. Anomalous features that appear in the experiments are analyzed according to theoretical models that describe the modulation of the interference pattern by temperature and built-in electric fields.PACS numbers: 71.35.Ji, 73.21.La, 78.20.Ls, 78.67.Hc The nanoscale ring structures, or quantum rings (QRs), have attracted the interest of the scientific community due to their unique rotational symmetry and the possibility to verify quantum mechanical phenomena.[1, 2, 3] Among these, the study of Aharonov-Bohm (AB)-like effects has gained a significant impetus, [4,5,6] and these efforts have gone beyond the original discussion of the AB interpretation on the nature of electromagnetic potentials and their role in quantum mechanics. [7] It is reasonable to say that the study of coherent interference occurring in transport properties of nanoscopic QRs, as proposed in Ref. 7 encounters, at the moment, serious scale limitations which has encouraged the search for optical implications associated to AB-effects.These endeavors applied to nanoscopic QRs do not strictly meet the original conditions for the ABconfiguration since the carriers are confined within regions with finite values of magnetic field. However, we still consider an observed effect as of AB-type if it can be explained assuming that the magnetic field is ideally concentrated in the middle of the QRs, i. e., when such effect comes essentially from potential vector-mediated quantum interference. As also considered in Ref. 8, in stationary systems this interference is generally reflected in a boundary condition and it is not as explicit as in the famous picture of an AB scattering situation.In this work we consider AB-interference in excitonic states as proposed theoretically in Refs. 9, 10, 12. Instead of looking only at the oscillatory dependence on magnetic flux of the electron-hole (e − h) recombination energy during photo-luminescence (PL), we also consider the excitonic oscillator strength whose oscillatory behavior reflects directly the changes in the exciton wavefunction as the magnetic flux increases. A similar experimental work was reported in Ref. 6 for type-II QRs, however, here we study type-I systems where both electron and hole move in the ring so that the correlation between them is crucial to the oscillatory behavior found in the PL integrated intensity. The samples studied here were grown using a RIBER 32P solid-source molecular beam epitaxy chamber and the QRs were grown using the following procedure. A 0.5 µm GaAs buffer layer was grown on semi-insulating (100) GaAs substrates at 580• C, after oxide desorption. Then, it was followed by 2.2 ML of InAs and the formation of quantum dots (QDs) at 520• C. The dots were obtained using the Stranski-Krastanov growth mode. Cycles of 0.14 ML of InAs plus a 2 s interruption under As 2 flux were r...

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Photocurrent spectroscopy of intersubband transitions in GaInAsN/(Al)GaAs asymmetric quantum well infrared photodetectors

Interdot coupling in (In,Ga)As/GaAs quantum dot arrays is studied by means of steady state and time-resolved photoluminescence (PL). A peculiar dependence of the PL decay time on the excitation and detection energy is revealed and ascribed to the peculiarities of the carrier and energy relaxation caused by both immediate electronic interdot coupling and long-range coupling through the radiation field.

Considering the Gross-Pitaevskii integral equation we are able to formally obtain an analytical solution for the order parameter Φ(x) and for the chemical potential µ as a function of a unique dimensionless non-linear parameter Λ. We report solutions for different range of values for the repulsive and the attractive non-linear interactions in the condensate. Also, we study a bright soliton-like variational solution for the order parameter for positive and negative values of Λ.Introducing an accumulated error function we have performed a quantitative analysis with other well-established methods as: the perturbation theory, the Thomas-Fermi approximation, and the numerical solution. This study gives a very useful result establishing the universal range of the Λ-values where each solution can be easily implemented. In particular we showed that for Λ < −9, the bright soliton function reproduces the exact solution of GPE wave function.