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The recombination dynamics are studied in viscous electron–hole plasma, consisting of electrons and photo-generated heavy and light holes, formed in the high-mobility mesoscopic GaAs channel. It is shown that an increase in the pump power reduces the concentration and mobility of background electrons, which, in turn, slows down their recombination with photogenerated holes. At a critical pump power, the recombination time begins to decrease, which is a consequence of the transition of a viscous electron–hole plasma from the hydrodynamic regime to the Drude diffusive regime. The observed transition occurs when the scattering of electrons with disorder begins to dominate over electron–electron scattering, which leads to the transformation of an inhomogeneous Poiseuille charge flow into a homogeneous diffusion flow. As a result, an optical analogue of the Gurzhi effect has been found.

This paper discusses the combined effects of optical excitation power, interface roughness, lattice temperature, and applied magnetic fields on the spin coherence of excitonic states in GaAs/AlGaAs multiple quantum wells. For low optical powers, at lattice temperatures between 4 and 50 K, the scattering with acoustic phonons and short-range interactions appear as the main decoherence mechanisms. Statistical fluctuations of the band gap, however, become also relevant in this regime and we were able to deconvolute them from the decoherence contributions. The circularly polarized magneto-photoluminescence unveils a nonmonotonic tuning of the coherence for one of the spin components at low magnetic fields. This effect has been ascribed to the competition between short-range interactions and spin-flip scattering, modulated by the momentum relaxation time., This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES), Finance Code 001. The authors also acknowledge financial support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Grants No. 2013/18719-1, No. 2014/19142-2, and No. 2018/01914-0, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and National Science Foundation (NSF) Grant No. OIA-1457888. This work was also partially funded by Spanish MICINN under Grant No. PID2019-106088RB-C3. This work is also supported by European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 956548, project Quantimony.

A comprehensive study of excitonic complexes in high-quality GaAs quantum wells has been performed. The polarization-resolved photoluminescence results show exciton, biexciton, and trion emissions tuned by temperature, excitation power, and by an external magnetic field. Excitons and biexcitons show important differences in their dependence on the external field. While the Zeeman splitting of biexcitons depends monotonically on the magnetic field, with a nearly constant g-factor, the behaviour of the exciton energy splitting is nonmonotonic and includes an inversion of sign as a function of the magnetic field. More importantly, we observe that a trion resonance emerges at a finite magnetic field, and only appears at low laser excitation power and for σ+ polarization emission. The non-trivial dependence of the energy levels on the external magnetic field, together with the polarization selective trion emission, leads to an intricate exciton and trion dynamics, which can be reproduced by a set of coupled rate equations. Based on this theoretical approach, we show that a fast spin-flip process can lead to the spin-asymmetric emission, which reveals a contrasting spin-dynamics of excitonic complexes ruled by their charge.

Structure, standard and efficient methods in paper medical records are important for a successful implementation of computerised medical records. We have conducted a survey among 26 somatic hospitals in a Norwegian region regarding present routines and use of information technology in patients records. The hospitals use six different patient administration systems, six laboratory, six radiology, and approximately 20 different specialist systems. 16 hospitals use three different electronic journal/documentation systems. Ten hospitals use the Word word processor for patient records. The full potential of word processing is not utilised. Digital dictation is seldom used; few hospitals have 24-hours service for documentation, and information technology is not used for documentation in nursing care. Four hospitals use microfilm. The survey shows that improvement is needed in order to achieve coordinated and effective use of information technology and manual routines in hospital medical records.