Resonant optical pumping of a Mn spin in a strain free quantum dot

We report on the spin properties of individual Mn atoms in II-VI semiconductor strain free quantum dots. Strain free Mn-doped CdTe quantum dots are formed by width fluctuations in thin quantum wells lattice matched on a CdTe substrate. These quantum dots permit to optically probe and address any spin state of a Mn atom in a controlled strain environment. The absence of strain induced magnetic anisotropy prevents an optical pumping of the Mn spin at zero magnetic field. Thus, a large photoluminescence is obtained under resonant optical excitation of the exciton-Mn complex. An efficient optical pumping of the coupled electronic and nuclear spins of the Mn is restored under a weak magnetic field. The observed reduction of the resonant photoluminescence intensity under magnetic field is well described by a model including the hyperfine coupling and a residual crystal field splitting of the Mn atom. Finally, we show that the second order correlation function of the resonant photoluminescence presents a large photon bunching at short delay which is a probe of the dynamics of coupled electronic and nuclear spins of the Mn atom

Spin dynamics of a Mn atom in a semiconductor quantum dot under resonant optical excitation

We analyze the spin dynamics of an individual magnetic atom (Mn) inserted in a II-VI semiconductor quantum dot under resonant optical excitation. In addition to standard optical pumping expected for a resonant excitation, we show that for particular conditions of laser detuning and excitation intensity, the spin population can be trapped in the state which is resonantly excited. This effect is modeled considering the coherent spin dynamics of the coupled electronic and nuclear spin of the Mn atom optically dressed by a resonant laser field. This spin population trapping mechanism is controlled by the combined effect of the coupling with the laser field and the coherent interaction between the different Mn spin states induced by an anisotropy of the strain in the plane of the quantum dot

Dynamics of a Mn spin coupled to a single hole confined in a quantum dot

Using the emission of the positively charged exciton as a probe, we analyze the dynamics of the optical pumping and the dynamics of the relaxation of a Mn spin exchange-coupled with a confined hole spin in a II-VI semiconductor quantum dot. The hole-Mn spin can be efficiently initialized in a few tens of $ns$ under optical injection of spin polarized carriers. We show that this optical pumping process and its dynamics are controlled by electron-Mn flip-flops within the positively charged exciton-Mn complex. The pumping mechanism and its magnetic field dependence are theoretically described by a model including the dynamics of the electron-Mn complex in the excited state and the dynamics of the hole-Mn complex in the ground state of the positively charged quantum dot. We measure at zero magnetic field a spin relaxation time of the hole-Mn spin in the $\mu s$ range or shorter. This hole-Mn spin relaxation is induced by the presence of valence band mixing in self-assembled quantum dots

Strain induced coherent dynamics of coupled carriers and Mn spins in a quantum dot

We report on the coherent dynamics of the spin of an individual magnetic atom coupled to carriers in a semiconductor quantum dot which has been investigated by resonant photoluminescence of the positively charged exciton (X+). We demonstrate that a positively charged CdTe/ZnTe quantum dot doped with a single Mn atom forms an ensemble of optical Lambda systems which can be addressed independently. We show that the spin dynamics of the X+Mn complex is dominated by the electron-Mn exchange interaction and report on the coherent dynamics of the electron-Mn spin system that is directly observed in the time domain. Quantum beats reflecting the coherent transfer of population between electron-Mn spin states, which are mixed by an anisotropic strain in the plane of the quantum dot, are clearly observed. We finally highlight that this strain induced coherent coupling is tunable with an external magnetic field

Resonant photoluminescence and dynamics of a hybrid Mn-hole spin in a positively charged magnetic quantum dot

We analyze, through resonant photoluminescence, the spin dynamics of an individual magnetic atom (Mn) coupled to a hole in a semiconductor quantum dot. The hybrid Mn-hole spin and the positively charged exciton in a CdTe/ZnTe quantum dot forms an ensemble of $\Lambda$ systems which can be addressed optically. Auto-correlation of the resonant photoluminescence and resonant optical pumping experiments are used to study the spin relaxation channels in this multilevel spin system. We identified for the hybrid Mn-hole spin an efficient relaxation channel driven by the interplay of the Mn-hole exchange interaction and the coupling to acoustic phonons. We also show that the optical $\Lambda$ systems are connected through inefficient spin-flips than can be enhanced under weak transverse magnetic field. The dynamics of the resonant photoluminescence in a p-doped magnetic quantum dot is well described by a complete rate equation model. Our results suggest that long lived hybrid Mn-hole spin could be obtained in quantum dot systems with large heavy-hole/light-hole splitting

Optical Stark Effect and Dressed Excitonic States in a Mn-doped Quantum Dot

We report on the observation of spin dependent optically dressed states and optical Stark effect on an individual Mn spin in a semiconductor quantum dot. The vacuum-to-exciton or the exciton-to-biexciton transitions in a Mn-doped quantum dot are optically dressed by a strong laser field and the resulting spectral signature is measured in photoluminescence. We demonstrate that the energy of any spin state of a Mn atom can be independently tuned using the optical Stark effect induced by a control laser. High resolution spectroscopy reveals a power, polarization and detuning dependent Autler-Townes splitting of each optical transition of the Mn-doped quantum dot. This experiment demonstrates a complete optical resonant control of the exciton-Mn system

Alternative ecological and social proposals for preventing the global threat of emerging infectious diseases.

Emerging infectious diseases are a major global health threat in the human, animal and plant worlds. Zoonoses and vector borne diseases are becoming prevalent worldwide. A large part of global health funding is dedicated to the fight against Dengue, Zika, or Ebola. Until now, public health strategies have been mainly based on vaccine development, medication testing or on proposals for “acceptable” cultural changes in local population practices to limit transmission risk, without thinking about the root causes. In this literature review, it will be argued that the current economic system, through its growth imperatives which ignore planetary limits, together with intensive agricultural practices, is related to infectious disease emergence. Monocultural practices, such as rubber/palm oil industrial plantations, through the ecological perturbation inflicted, act as a driver of vector borne and zoonotic diseases. Deforestation, loss of biodiversity, and human invasion of remote forested areas are followed by the emergence of zoonoses such as Ebola disease. Even if any emergence is always a multifactorial process, it is still fundamental to highlight the major influence of environmental drivers. The characteristics of specific ecological and social contexts within which emergence occurs should be explored. Alternative health and environmental paradigms could help impede the emergence of infectious diseases.  A true “One health” approach which takes care of ecosystems and preserves the diversity of living things and of relationships corresponds to an “EcoHealth” approach. Ecological options and environmental solutions could produce a real innovation in public health. Stopping deforestation and ecosystem destruction and fostering peasant agroecology and free evolution for certain forested areas could slowly lead to rebalanced ecosystems. Furthermore, ecological actions would be less stigmatizing than promotion of cultural changes. An alternative public health program based on “health within a healthy environment” would be more effective than a secondary struggle against emerging diseases. This suggests introducing public health as a fundamental land use issue, inaugurating peasant agroecology, land use and conservation as fundamental public health issues, and developing coherent policies.  Key words: emerging infectious diseases, EcoHealth, pathogenic environment, plantacionocene, ecological alternatives, Planetary Health, ecosystemic approach to public healt

Le Geopark beaujolais : émergence d'un nouvel objet dans la recomposition territoriale

International audienceThis communication, based on reflexions on a work in research-action since 2014 and on an active territorial project since 2012, provides a point of view and an analysis of territorialisation processes within the frame of a new territorial object: the aspiring Geopark Beaujolais. Both a label and a territorial-planning project, this new territorial form was born in a context of territorial reorganization, within which the Pays Beaujolais is being changed, particularly by the creation of Lyons’ metropolis. The territorial object “Geopark” proceeds from the demand of territorial stakeholders, from institutions to associations and the private sphere. This new hybrid form, between conservation of natural heritage and local development, questions again the links between rural space and metropolis.Cet article, issu de la réflexion d’un travail de recherche-action initié en 2014 et d’une démarche-projet active et suivie depuis 2012, propose un point de vue et une analyse des processus de territorialisation dans le cadre de la genèse d’un nouvel objet territorial, le Geopark en Beaujolais. À la fois label et projet d’aménagement sur l’ensemble d’un territoire, cette nouvelle forme territoriale naît dans un contexte de recomposition territoriale, dans laquelle le Pays Beaujolais est bouleversé, notamment par la création de la métropole du Grand Lyon. L’objet territorial qu’est Geopark émane véritablement d’une demande des acteurs du territoire, qu’ils soient institutionnels, associatifs ou privés. Cette nouvelle forme hybride, entre conservation des patrimoines naturels et développement local, réinterroge les rapports entre espace rural et métropole