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DOI: 10.1109/IRMMW-THz.2018.8510039
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We report on the temperature-dependent magneto absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells above the critical well thickness d(c). Our results, obtained in magnetic fields up to 16 T and temperature range from 1.7 to 150 K, clearly indicate a change in the band-gap energy with temperature. A topological phase transition between quantum spin Hall and trivial insulator states, revealing appearance of single-valley Dirac fermions at T = 27 and 90 K for 6.5 and 8 nm QWs respectively, was clearly observed in our magnetospectroscopy measurements.

Commentaires: 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), Nagoya, JAPAN, SEP 09-14, 2018

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Increasing the data rates of wireless communicationsrequires to increase the carrier frequency to hundred’s of GHz,thus emitters and detectors that can operate at high data ratesare required. We review a possible source and receiver that canbeen used for THz communications. We present a photonic-basedemitter that provides a coherent THz signal in the 50–700+ GHz,based on the excitation of a uni-travelling carrier photodiodeby a two-frequency semiconductor laser that operates on twotransverse modes. The performance of THz detectors basedon GaAs field-effect transistors are also presented, along withcommunications using direct amplitude modulation at 8.3 Gbpsand an heterodyne communication at 1.5 Gbps.

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DOI: 10.1103/physrevx.8.031061
WoS: 000444211800003
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We describe the activation of out-of-equilibrium collective oscillations of a macromolecule as a classical phonon condensation phenomenon. If a macromolecule is modeled as an open system-that is, it is subjected to an external energy supply and is in contact with a thermal bath to dissipate the excess energy-the internal nonlinear couplings among the normal modes make the system undergo a nonequilibrium phase transition when the energy input rate exceeds a threshold value. This transition takes place between a state where the energy is incoherently distributed among the normal modes and a state where the input energy is channeled into the lowest-frequency mode entailing a coherent oscillation of the entire molecule. The model put forward in the present work is derived as the classical counterpart of a quantum model proposed a long time ago by Fröhlich in an attempt to explain the huge speed of enzymatic reactions. We show that such a phenomenon is actually possible. Two different and complementary THz near-field spectroscopic techniques-a plasmonic rectenna and a microwire near-field probe-have been used in two different labs to eliminate artifacts. By considering an aqueous solution of a model protein, the bovine serum albumin, we find that this protein displays a remarkable absorption feature around 0.314 THz, when driven in a stationary out-of-thermal equilibrium state by means of optical pumping. The experimental outcomes are in very good qualitative agreement with the theory developed in the first part of the paper and in excellent quantitative agreement with the theoretical result, allowing us to identify the observed spectral feature with a collective oscillation of the entire molecule.

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Une étude sur la caractérisation de bois tropicaux (la grenadille) pour la facture d’instruments à vent est en cours dans le cadre d’une collaboration entre Henri SELMER Paris et le LMGC. Les recherches portent actuellement sur la diffusion de l’eau dans des échantillons de bois de différentes espèces et présentant des formes variées (cylindriques, parallélépipédiques, autres...), la modélisation de la teneur en eau à l’équilibre (EMC) sous diverses conditions atmosphériques, la mesure des coefficients de retrait et gonflement du bois au cours de changement de teneur en eau, et la validation d’un modèle de diffusion en utilisant l’imagerie TéraHertz (THz).

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DOI: 10.1088/1361-648X/aaebf5
WoS: WOS:000450901400001
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