Uncoupled excitons in semiconductor microcavities detected in resonant Raman scattering

We present an outgoing resonant Raman-scattering study of a GaAs/AlGaAs based microcavity embedded in a p-i-n junction. The p-i-n junction allows the vertical electric field to be varied, permitting control of exciton-photon detuning and quenching of photoluminescence which otherwise obscures the inelastic light scattering signals. Peaks corresponding to the upper and lower polariton branches are observed in the resonant Raman cross sections, along with a third peak at the energy of uncoupled excitons. This third peak, attributed to disorder activated Raman scattering, provides clear evidence for the existence of uncoupled exciton reservoir states in microcavities in the strong-coupling regime

Quantum-fluid dynamics of microcavity polaritons

Semiconductor microcavities offer a unique system to investigate the physics of weakly interacting bosons. Their elementary excitations, polaritons--a mixture of excitons and photons--behave, in the low density limit, as bosons that can undergo a phase transition to a regime characterised by long range coherence. Condensates of polaritons have been advocated as candidates for superfluidity; and the formation of vortices as well as elementary excitations with a linear dispersion are actively sought after. In this work, we have created and set in motion a macroscopically degenerate state of polaritons and let it collide with a variety of defects present in the sample. Our experiments show striking manifestations of a coherent light-matter packet that displays features of a superfluid, although one of a highly unusual character as it involves an out-of-equilibrium dissipative system where it travels at ultra-fast velocity of the order of 1% the speed of light. Our main results are the observation of i) a linear polariton dispersion accompanied with diffusion-less motion, ii) flow without resistance when crossing an obstacle, iii) suppression of Rayleigh scattering and iv) splitting into two fluids when the size of the obstacle is comparable with the size of the wavepacket. This work opens the way to the investigation of new phenomenology of out-of-equilibrium condensates.Comment: 22 pages, 5 figure

The Cerenkov effect revisited: from swimming ducks to zero modes in gravitational analogs

We present an interdisciplinary review of the generalized Cerenkov emission of radiation from uniformly moving sources in the different contexts of classical electromagnetism, superfluid hydrodynamics, and classical hydrodynamics. The details of each specific physical systems enter our theory via the dispersion law of the excitations. A geometrical recipe to obtain the emission patterns in both real and wavevector space from the geometrical shape of the dispersion law is discussed and applied to a number of cases of current experimental interest. Some consequences of these emission processes onto the stability of condensed-matter analogs of gravitational systems are finally illustrated.Comment: Lecture Notes at the IX SIGRAV School on "Analogue Gravity" in Como, Italy from May 16th-21th, 201

In-plane propagation of excitonic cavity polaritons

International audienceBy exciting resonantly a microcavity with a pulsed laser beam, we have observed the in-plane propagation of excitonic cavity polaritons over distances much greater than the wavelength. The initial in-plane wave vector is conserved during the propagation, showing that it is a good quantum number for cavity polaritons. The polariton group velocities were measured as a function of both the in-plane wave vector and detuning. Propagation is faster for negative detunings where the polaritons have a light effective mass. The observations are in good agreement with a simple two-oscillator model

Personalidad y percepción de dolor en fibromialgia: Un estudio piloto de casos y controles

Mediante el presente estudio se pretende evaluar la influencia de los rasgos de personalidad en el grado y tipología de dolor referido. Muestra: 80 participantes, todas ellas mujeres de edades comprendidas entre los 31 y los 63 años de edad, divididas en dos grupos, grupo Fibromialgia (FM) y grupo control. Material y método: Se administró el Cuestionario de Impacto de la Fibromialgia (FIQ) para evaluar el impacto de la FM,  el Inventario de Temperamento y Carácter – Revisado de Cloninger (TCI-R) para evaluar las dimensiones de la personalidad y el Cuestionario del Dolor de McGill (MPQ) para la evaluación de la percepción de dolor inducido mecánicamente. Resultados: Se observan diferencias entre el grupo FM y el grupo control en la valoración del dolor y en las dimensiones Búsqueda de novedad (BN), Evitación del daño (ED) y Autodirección (AD). Además, se constata que las dimensiones de la personalidad ED (p = 0,00) y Cooperación (COOP) (p = 0,12) correlacionan significativamente con la percepción de dolor en el grupo FM. CONCLUSIONES. Se objetiva que existen diferencias en los rasgos de personalidad y percepción de dolor inducido entre FM y el grupo control y, aunque no explica el total de la varianza, se halla que los rasgos  de  personalidad  ED y COOP permiten predecir el nivel y tipología de dolor referido con una varianza total explicada del 21%

How can promotion agencies impact SME internationalisation ? The case of the French company SLAT

International audienceThis chapter focuses on the international development of SLAT, an independent SME which develops, produces and markets solutions of secured alimentations. Located in France, the company has more than 70 employees. The SME has mainly developed in international markets through export activities: in 2016, it realised 21.2% of its total sales abroad and its products were marketed in 37 countries. In 2011, the company decided to implement a sales subsidiary in Germany to strengthen its presence in international markets. In this process, the company was accompanied by a promotion agency which helps companies from the Auvergne-Rhône-Alpes region to expand into foreign markets. The authors of this chapter explain the role played by the agency in the establishment of the foreign subsidiary and the influence of a successful accompaniment experience on the internationalisation process