Search

Your search keyword '"L. Bouet"' showing total 38 results
Start Over Author "L. Bouet"
38 results on '"L. Bouet"'

1. Hyperfine coupling of hole and nuclear spins in symmetric (111)-grown GaAs quantum dots

Author

P. Zhou, Takaaki Mano, Xavier Marie, Mikhail M. Glazov, Thierry Amand, E. L. Ivchenko, Bernhard Urbaszek, Marta L. Vidal, L. Bouet, Gang Wang, Kazuaki Sakoda, Takashi Kuroda, Mikhail V. Durnev, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), National Institute for Materials Science (NIMS), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Zeeman effect, Spin polarization, Condensed matter physics, Spins, Quantum dots, 02 engineering and technology, Electron, Spintronics, 021001 nanoscience & nanotechnology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, symbols.namesake, Quantum dot, 0103 physical sciences, symbols, Heterostructures, [CHIM]Chemical Sciences, Trion, 010306 general physics, 0210 nano-technology, Spin (physics), Hyperfine structure, Photoluminescence
Abstract

© 2016 American Physical Society. In self-assembled III-V semiconductor quantum dots, valence holes have longer spin coherence times than the conduction electrons, due to their weaker coupling to nuclear spin bath fluctuations. Prolonging hole spin stability relies on a better understanding of the hole to nuclear spin hyperfine coupling which we address both in experiment and theory in the symmetric (111) GaAs/AlGaAs droplet dots. In magnetic fields applied along the growth axis, we create a strong nuclear spin polarization detected through the positively charged trion X+ Zeeman and Overhauser splittings. The observation of four clearly resolved photoluminescence lines - a unique property of the (111) nanosystems - allows us to measure separately the electron and hole contribution to the Overhauser shift. The hyperfine interaction for holes is found to be about five times weaker than that for electrons. Our theory shows that this ratio depends not only on intrinsic material properties but also on the dot shape and carrier confinement through the heavy-hole mixing, an opportunity for engineering the hole-nuclear spin interaction by tuning dot size and shape.

Published
2016

2. Magnetospectroscopy of excited states in charge-tunable GaAs/AlGaAs [111] quantum dots

Author

Mikhail M. Glazov, Kazuaki Sakoda, Mikhail V. Durnev, Thierry Amand, Neul Ha, P. Zhou, Bernhard Urbaszek, Marta L. Vidal, Gang Wang, Takashi Kuroda, E. L. Ivchenko, L. Bouet, Xavier Marie, Takaaki Mano, A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), National Institute for Materials Science (NIMS), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Photoluminescence, Exciton, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Condensed Matter::Materials Science, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Coulomb, 010306 general physics, Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Condensed Matter - Mesoscale and Nanoscale Physics, Quantum dots, Magneto-optical spectra, Exchange interaction, Charge (physics), Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, 3. Good health, Quantum dot, Excited state, Excitons, Charge carrier, Atomic physics, 0210 nano-technology
Abstract

We present a combined experimental and theoretical study of highly charged and excited electron-hole complexes in strain-free (111) GaAs/AlGaAs quantum dots grown by droplet epitaxy. We address the complexes with one of the charge carriers residing in the excited state, namely, the ``hot'' trions X$^{-*}$ and X$^{+*}$, and the doubly negatively charged exciton X$^{2-}$. Our magneto-photoluminescence experiments performed on single quantum dots in the Faraday geometry uncover characteristic emission patterns for each excited electron-hole complex, which are very different from the photoluminescence spectra observed in (001)-grown quantum dots. We present a detailed theory of the fine structure and magneto-photoluminescence spectra of X$^{-*}$, X$^{+*}$ and X$^{2-}$ complexes, governed by the interplay between the electron-hole Coulomb exchange interaction and the heavy-hole mixing, characteristic for these quantum dots with a trigonal symmetry. Comparison between experiment and theory of the magneto-photoluminescence allows for precise charge state identification, as well as extraction of electron-hole exchange interaction constants and $g$-factors for the charge carriers occupying excited states., 12 pages, 5 figures

Published
2016

3. Magneto-optics in transition metal diselenide monolayers

Author

Gang Wang, Xavier Marie, E. L. Ivchenko, Bernhard Urbaszek, Thierry Amand, L. Bouet, Mikhail M. Glazov, E. Palleau, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Photoluminescence, Materials science, Exciton, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Molecular physics, Diselenide, symbols.namesake, Condensed Matter::Materials Science, 0103 physical sciences, [CHIM]Chemical Sciences, General Materials Science, 010306 general physics, Condensed Matter::Quantum Gases, Condensed Matter - Materials Science, Zeeman effect, Condensed Matter::Other, Mechanical Engineering, Materials Science (cond-mat.mtrl-sci), General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Polarization (waves), Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Magnetic field, Mechanics of Materials, symbols, Trion, 0210 nano-technology, Excitation
Abstract

We perform photoluminescence experiments at 4K on two different transition metal diselenide monolayers, namely MoSe2 and WSe2 in magnetic fields $B_z$ up to 9T applied perpendicular to the sample plane. In MoSe2 monolayers the valley polarization of the neutral and the charged exciton (trion) can be tuned by the magnetic field, independent of the excitation laser polarization. In the investigated WSe2 monolayer sample the evolution of the trion valley polarization depends both on the applied magnetic field and the excitation laser helicity, while the neutral exciton valley polarization depends only on the latter. Remarkably we observe a reversal of the sign of the trion polarization between WSe2 and MoSe2. For both systems we observe a clear Zeeman splitting for the neutral exciton and the trion of about $\pm2$meV at $B_z\mp9$T. The extracted Land\'{e}-factors for both exciton complexes in both materials are $g\approx -4$., Comment: 9 pages, 2 figures

Published
2015

4. Giant Enhancement of the Optical Second-Harmonic Emission ofWSe2Monolayers by Laser Excitation at Exciton Resonances

Author

Andrea Balocchi, Gang Wang, Xavier Marie, Iann C. Gerber, Delphine Lagarde, Bernhard Urbaszek, Marta L. Vidal, Thierry Amand, and L. Bouet

Subjects
Materials science, Exciton, Superlattice, General Physics and Astronomy, 02 engineering and technology, 021001 nanoscience & nanotechnology, Laser, 01 natural sciences, law.invention, Condensed Matter::Materials Science, law, 0103 physical sciences, Monolayer, Harmonic, Atomic physics, 010306 general physics, 0210 nano-technology, Biexciton, Excitation, Laser beams
Abstract

A three-order of magnitude increase in the optical second-harmonic emission of WSe${}_{2}$ monolayers is detected by tuning the exciting laser beam to the WSe${}_{2}$ exciton resonances.

Published
2015

5. Giant enhancement of the optical second-harmonic emission of WSe(2) monolayers by laser excitation at exciton resonances

Author

G, Wang, X, Marie, I, Gerber, T, Amand, D, Lagarde, L, Bouet, M, Vidal, A, Balocchi, and B, Urbaszek

Abstract

We show that the light-matter interaction in monolayer WSe_{2} is strongly enhanced when the incoming electromagnetic wave is in resonance with the energy of the exciton states of strongly Coulomb bound electron-hole pairs below the electronic band gap. We perform second harmonic generation (SHG) spectroscopy as a function of laser energy and polarization at T=4 K. At the exciton resonance energies we record an enhancement by up to 3 orders of magnitude of the SHG efficiency, due to the unusual combination of electric dipole and magnetic dipole transitions. The energy and parity of the exciton states showing the strong resonance effects are identified in 1- and 2-photon photoluminescence excitation experiments, corroborated by first principles calculations. Targeting the identified exciton states in resonant 2-photon excitation allows us to maximize k-valley coherence and polarization.

Published
2014

7. Exciton fine structure and spin decoherence in monolayers of transition metal dichalcogenides

Author

Thierry Amand, Mikhail M. Glazov, L. Bouet, Bernhard Urbaszek, Xavier Marie, Delphine Lagarde, A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)

Subjects
Quantum decoherence, Exciton, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Condensed Matter::Materials Science, Transition metal, Electric field, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, 010306 general physics, Biexciton, Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Condensed Matter::Other, Exchange interaction, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Polarization (waves), 3. Good health, Electronic, Optical and Magnetic Materials, Picosecond, 0210 nano-technology
Abstract

We study the neutral exciton energy spectrum fine structure and its spin dephasing in transition metal dichalcogenides such as MoS$_2$. The interaction of the mechanical exciton with its macroscopic longitudinal electric field is taken into account. The splitting between the longitudinal and transverse excitons is calculated by means of the both electrodynamical approach and $\mathbf k \cdot \mathbf p$ perturbation theory. This long-range exciton exchange interaction can induce valley polarization decay. The estimated exciton spin dephasing time is in the picosecond range, in agreement with available experimental data., Comment: 5 pages, 3 figures

Published
2014

9. Nuclear magnetization in gallium arsenide quantum dots at zero magnetic field

Author

Kazuaki Sakoda, Takaaki Mano, G. Sallen, Olivier Krebs, Thierry Amand, S. Kunz, Bernhard Urbaszek, Daniel Paget, L. Bouet, Xavier Marie, Takashi Kuroda, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), National Institute for Materials Science (NIMS), Laboratoire de physique de la matière condensée (LPMC), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de photonique et de nanostructures (LPN), Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear Theory, FOS: Physical sciences, General Physics and Astronomy, 7. Clean energy, Article, General Biochemistry, Genetics and Molecular Biology, Gallium arsenide, Condensed Matter::Materials Science, chemistry.chemical_compound, Magnetization, Optical physics, Nuclear magnetic resonance, Semiconductor quantum dots, Magnetic properties and materials, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Nuclear Experiment, Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Multidisciplinary, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Quantum dots, General Chemistry, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Polarization (waves), Magnetic field, Applied physics, chemistry, Optical control, Quantum dot, Quadrupole, Condensed Matter::Strongly Correlated Electrons
Abstract

Optical and electrical control of the nuclear spin system allows enhancing the sensitivity of NMR applications and spin-based information storage and processing. Dynamic nuclear polarization in semiconductors is commonly achieved in the presence of a stabilizing external magnetic field. Here we report efficient optical pumping of nuclear spins at zero magnetic field in strain-free GaAs quantum dots. The strong interaction of a single, optically injected electron spin with the nuclear spins acts as a stabilizing, effective magnetic field (Knight field) on the nuclei. We optically tune the Knight field amplitude and direction. In combination with a small transverse magnetic field, we are able to control the longitudinal and transverse components of the nuclear spin polarization in the absence of lattice strain—that is, in dots with strongly reduced static nuclear quadrupole effects, as reproduced by our model calculations., Optical control of nuclear spin polarization in semiconductor quantum dots is promising for applications in NMR imaging. Sallen et al. report efficient dynamic nuclear polarization at zero magnetic field in strain-free gallium arsenide quantum dots with Knight fields dominating the nuclear quadrupole effects.

Published
2014

10. Carrier and Polarization Dynamics in MonolayerMoS2

Author

Ping-Heng Tan, Bilu Liu, Thierry Amand, Bernhard Urbaszek, C. Zhu, Delphine Lagarde, Xavier Marie, and L. Bouet

Subjects
Polarization rotator, Photoluminescence, Materials science, Band gap, business.industry, Exciton, General Physics and Astronomy, 02 engineering and technology, Photon energy, 021001 nanoscience & nanotechnology, Polarization (waves), 01 natural sciences, Optics, 0103 physical sciences, Direct and indirect band gaps, Laser power scaling, Atomic physics, 010306 general physics, 0210 nano-technology, business
Abstract

In monolayer ${\mathrm{MoS}}_{2}$, optical transitions across the direct band gap are governed by chiral selection rules, allowing optical valley initialization. In time-resolved photoluminescence (PL) experiments, we find that both the polarization and emission dynamics do not change from 4 to 300 K within our time resolution. We measure a high polarization and show that under pulsed excitation the emission polarization significantly decreases with increasing laser power. We find a fast exciton emission decay time on the order of 4 ps. The absence of a clear PL polarization decay within our time resolution suggests that the initially injected polarization dominates the steady-state PL polarization. The observed decrease of the initial polarization with increasing pump photon energy hints at a possible ultrafast intervalley relaxation beyond the experimental ps time resolution. By compensating the temperature-induced change in band gap energy with the excitation laser energy, an emission polarization of 40% is recovered at 300 K, close to the maximum emission polarization for this sample at 4 K.

Published
2014

12. Valley dynamics probed through charged and neutral exciton emission in monolayer WSe2

Author

Gang Wang, D. Lagarde, Andrea Balocchi, Xavier Marie, B. Urbaszek, M. Vidal, Thierry Amand, and L. Bouet

Subjects
Physics, Condensed Matter::Quantum Gases, Photoluminescence, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter::Other, Exciton, FOS: Physical sciences, Position and momentum space, Electron, Condensed Matter Physics, Polarization (waves), Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Transition metal, Monolayer, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Atomic physics, Trion
Abstract

Optical interband transitions in monolayer transition metal dichalcogenides such as WSe2 and MoS2 are governed by chiral selection rules. This allows efficient optical initialization of an electron in a specific K-valley in momentum space. Here we probe the valley dynamics in monolayer WSe2 by monitoring the emission and polarization dynamics of the well separated neutral excitons (bound electron hole pairs) and charged excitons (trions) in photoluminescence. The neutral exciton photoluminescence intensity decay time is about 4ps, whereas the trion emission occurs over several tens of ps. The trion polarization dynamics shows a partial, fast initial decay within tens of ps before reaching a stable polarization of about 20%, for which a typical valley polarization decay time larger than 1ns can be inferred. This is a clear signature of stable, optically initialized valley polarization., Comment: 16 pages, 9 figures

Published
2014
Full Text
View/download PDF

13. Exciton dynamics in WSe2 bilayers

Author

Bernhard Urbaszek, Marta L. Vidal, Delphine Lagarde, Gang Wang, Thierry Amand, Andrea Balocchi, Xavier Marie, and L. Bouet

Subjects
Condensed Matter - Materials Science, Photoluminescence, Materials science, Physics and Astronomy (miscellaneous), Exciton, Physics::Optics, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, 02 engineering and technology, 021001 nanoscience & nanotechnology, Polarization (waves), Laser, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, law.invention, Brillouin zone, Condensed Matter::Materials Science, law, 0103 physical sciences, Atomic physics, 010306 general physics, 0210 nano-technology, Spectroscopy, Excitation, Energy (signal processing)
Abstract

We investigate exciton dynamics in 2H-WSe2 bilayers in time-resolved photoluminescence (PL) spectroscopy. Fast PL emission times are recorded for both the direct exciton with $\tau_{D}$ ~ 3 ps and the indirect optical transition with $\tau_{i}$ ~ 25 ps. For temperatures between 4 to 150 K $\tau_{i}$ remains constant. Following polarized laser excitation, we observe for the direct exciton transition at the K point of the Brillouin zone efficient optical orientation and alignment during the short emission time $\tau_{D}$. The evolution of the direct exciton polarization and intensity as a function of excitation laser energy is monitored in PL excitation (PLE) experiments., Comment: 4 pages, 3 figures

Published
2014
Full Text
View/download PDF

14. Suppression of crack formation in garnet film by using a compound glass underlayer

Author

A. Furuya, C. Baubet, Takaya Tanabe, Hiroshi Yoshikawa, Lionel Presmanes, M. Yamamoto, Abel Rousset, L. Bouet, Philippe Tailhades, and C. Despax

Subjects
Fabrication, Materials science, business.industry, Fissure, Crystal structure, Coercivity, Magnetic hysteresis, Thermal expansion, Electronic, Optical and Magnetic Materials, Optics, medicine.anatomical_structure, Sputtering, medicine, Electrical and Electronic Engineering, Composite material, Thin film, business
Abstract

Garnet film made as a magneto-optical medium suffers from the problem of crack formation, caused by the high temperature of the garnet film fabrication process. We solved this problem by using a compound glass with a yield point lower than the garnet heat-treatment temperature as an underlayer. This successfully suppressed the formation of cracks in the heat-treated garnet film. As a result, we obtained a garnet film recording medium with excellent crystalline structure and high coercive force.

Published
2001

15. Thin Films and Fine Powders of Ferrites : Materials for Magneto-Optical Recording Media

Author

Abel Rousset, Philippe Tailhades, L. Bouet, and Lionel Presmanes

Subjects
Materials science, business.industry, 020502 materials, Spinel, General Physics and Astronomy, 02 engineering and technology, engineering.material, Magneto optical, Metal, Wavelength, symbols.namesake, Optics, 0205 materials engineering, Transition metal, [PHYS.HIST]Physics [physics]/Physics archives, visual_art, Faraday effect, engineering, symbols, visual_art.visual_art_medium, Optoelectronics, Recording media, Thin film, business
Abstract

In the near future, the magneto-optical (MO) recording will require materials having high MO effects at short wavelengths (400-500 nm). Ferrites, especially garnets, but also spinel ferrites have highly advantageous MO properties in this spectrum and also have very stable structural and chemical properties. The present paper evaluates their used as MO media, in comparison with the rare-earth transition metals alloys and the metallic multilayers.

Published
1997

16. Carrier and polarization dynamics in monolayer MoS2

Author

D, Lagarde, L, Bouet, X, Marie, C R, Zhu, B L, Liu, T, Amand, P H, Tan, and B, Urbaszek

Abstract

In monolayer MoS2, optical transitions across the direct band gap are governed by chiral selection rules, allowing optical valley initialization. In time-resolved photoluminescence (PL) experiments, we find that both the polarization and emission dynamics do not change from 4 to 300 K within our time resolution. We measure a high polarization and show that under pulsed excitation the emission polarization significantly decreases with increasing laser power. We find a fast exciton emission decay time on the order of 4 ps. The absence of a clear PL polarization decay within our time resolution suggests that the initially injected polarization dominates the steady-state PL polarization. The observed decrease of the initial polarization with increasing pump photon energy hints at a possible ultrafast intervalley relaxation beyond the experimental ps time resolution. By compensating the temperature-induced change in band gap energy with the excitation laser energy, an emission polarization of 40% is recovered at 300 K, close to the maximum emission polarization for this sample at 4 K.

Published
2013

17. Voltage control of electron-nuclear spin correlation time in a single quantum dot

Author

Ian Farrer, Bernhard Urbaszek, Johan Nilsson, Thierry Amand, David A. Ritchie, S. Kunz, Anthony J. Bennett, L. Bouet, Richard Mark Stevenson, Xavier Marie, Andrew J. Shields, Toshiba Research Europe Ltd, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Cavendish Laboratory, University of Cambridge [UK] (CAM), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Hanle effect, Physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Spins, Condensed matter physics, Spin polarization, Condensed Matter - Mesoscale and Nanoscale Physics, Exciton, FOS: Physical sciences, 02 engineering and technology, Electron, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, 3. Good health, Electronic, Optical and Magnetic Materials, Magnetic field, Quantum dot, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), [CHIM]Chemical Sciences, Atomic physics, 010306 general physics, 0210 nano-technology, Hyperfine structure
Abstract

We demonstrate bias control of the hyperfine coupling between a single electron in an InAs quantum dot and the surrounding nuclear spins monitored through the positively charged exciton X+ emission. In applied longitudinal magnetic fields we vary simultaneously the correlation time of the hyperfine interaction and the nuclear spin relaxation time and thereby the amplitude of the achieved dynamic nuclear polarization under optical pumping conditions. In applied transverse magnetic fields a change in the applied bias allows to switch from the anomalous Hanle effect to the standard electron spin depolarization curves., 6 pages, 3 figures

Published
2013

18. Magnetic field induced valence band mixing in [111] grown semiconductor quantum dots

Author

Mikhail V. Durnev, Delphine Lagarde, S. Kunz, L. Bouet, Thierry Amand, Kazuaki Sakoda, Mikhail M. Glazov, G. Sallen, Takashi Kuroda, Xavier Marie, Bernhard Urbaszek, Masafumi Jo, E. L. Ivchenko, Takaaki Mano, A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), National Institute for Materials Science (NIMS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Band gap, Exciton, FOS: Physical sciences, 02 engineering and technology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Polarization (waves), 01 natural sciences, 3. Good health, Electronic, Optical and Magnetic Materials, Magnetic field, Quantum dot, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, [CHIM]Chemical Sciences, Emission spectrum, Microscopic theory, 010306 general physics, 0210 nano-technology, Mixing (physics)
Abstract

We present a microscopic theory of the magnetic field induced mixing of heavy-hole states +/- 3/2 in GaAs droplet dots grown on (111)A substrates. The proposed theoretical model takes into account the striking dot shape with trigonal symmetry revealed in atomic force microscopy. Our calculations of the hole states are carried out within the Luttinger Hamiltonian formalism, supplemented with allowance for the triangularity of the confining potential. They are in quantitative agreement with the experimentally observed polarization selection rules, emission line intensities and energy splittings in both longitudinal and transverse magnetic fields for neutral and charged excitons in all measured single dots., Comment: 11 pages, 6 figures

Published
2013

19. Relations between magneto-optical properties and reactivity in cobalt-manganese ferrite thin films and powders

Author

Abel Rousset, L. Bouet, and Philippe Tailhades

Subjects
Materials science, Spinel, chemistry.chemical_element, Manganese, engineering.material, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Ion, Wavelength, Nuclear magnetic resonance, Chemical engineering, chemistry, Oxidation state, engineering, Ferrite (magnet), Thin film, Cobalt
Abstract

Co-Mn spinel ferrites were prepared as submicron powders and thin films. Because of their finely divided state, these spinels could be oxidized at low temperatures to give novel cation-deficient ferrites. For these two material forms, the magneto-optical properties were found to be strongly dependent on the ferrite oxidation state. The highest coercivities and Faraday rotations were obtained when the ferrites were partially oxidized. These phenomena are attributed to the mechanical stress effect developed during the oxidation of the manganese ions. The properties of these ferrites could be of interest for magneto-optical recording applications. The first static recording tests were performed at 780 nm wavelength.

Published
1996

20. The role of cobalt in the oxidation mechanism modification of the Mo3+ ions of molybdenum-substituted magnetites

Author

E. Kester, Philippe Tailhades, Abel Rousset, L. Bouet, and Bernard Gillot

Subjects
Reaction mechanism, Inorganic chemistry, Spinel, chemistry.chemical_element, engineering.material, Condensed Matter Physics, Oxygen, Ion, chemistry.chemical_compound, chemistry, Octahedron, Ternary compound, Molybdenum, engineering, Physical and Theoretical Chemistry, Instrumentation, Cobalt
Abstract

A kinetic study of the oxidation of Mo 3+ ions has been performed on two submicrometer Mo and MoCo ferrites of spinel structure with a nearly identical molybdenum content. We show that for the Co-free sample, oxidation proceeds by cationic diffusion in a cation-deficient spinel with a variable chemical diffusion coefficient. For the Co sample, which showed a pronounced stability towards oxygen, the oxidation process was divided into three steps. In step I, oxidation declines with time in an initial period (degree of oxidation α α α > 0.25) oxidation is best described by the diffusion-controlled Jander equation. Comparing the vibrational spectra of these two spinels after total oxidation for various thermal treatments, we conclude that the coordination around Mo 6+ ions changes from tetrahedral to octahedral with Co substitution and that the location of cobalt and molybdenum ions in octahedral sites changes with the annealing process.

Published
1995

21. Robust optical emission polarization in MoS2monolayers through selective valley excitation

Author

Bilu Liu, Gang Wang, Xavier Marie, Wen-Peng Han, Yuan Lu, G. Sallen, Thierry Amand, Bernhard Urbaszek, Changxin Zhu, L. Bouet, and Ping-Heng Tan

Subjects
Condensed Matter - Materials Science, Photoluminescence, Materials science, business.industry, Graphene, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Position and momentum space, Condensed Matter Physics, Polarization (waves), Molecular physics, Electronic, Optical and Magnetic Materials, law.invention, Transverse magnetic, Optics, law, Monolayer, Optical emission spectroscopy, business, Excitation
Abstract

We report polarization resolved photoluminescence from monolayer MoS2, a two-dimensional, non-centrosymmetric crystal with direct energy gaps at two different valleys in momentum space. The inherent chiral optical selectivity allows exciting one of these valleys and close to 90% polarized emission at 4K is observed with 40% polarization remaining at 300K. The high polarization degree of the emission remains unchanged in transverse magnetic fields up to 9T indicating robust, selective valley excitation., Comment: 5 pages, 3 figures

Published
2012

22. Reactivity of the submicron molybdenum ferrites towards oxygen and formation of new cation deficient spinels

Author

Abel Rousset, Bruno Domenichini, L. Bouet, Ph. Tailhades, and Bernard Gillot

Subjects
Valence (chemistry), Inorganic chemistry, Spinel, chemistry.chemical_element, General Chemistry, engineering.material, Condensed Matter Physics, Ion, Thermogravimetry, Crystallography, Octahedron, X-ray photoelectron spectroscopy, chemistry, Molybdenum, engineering, General Materials Science, Qualitative inorganic analysis
Abstract

Valence states of molybdenum and iron ions and their cationic distribution on both octahedral (B) and tetrahedral (A) sites of the spinel structure of molybdenum-substituted magnetites, Fe3−xMoxO4, obtained by two ways (samples synthesized by w et process or ground samples synthesized by the ceramic route) and which are oxidized in cation deficient spinels, have been performed by derivative thermogravimetry (DTG), X-ray diffraction, IR and XPS spectrometries. It has been demonstrated that in the case of the samples synthesized by wet processes, the Fe2+B, Mo3+B, MO4+B, Fe2+A, Mo4+A ions are successiv ely oxidized into Fe3+B and Mo6+A ions below 530°C. For the samples synthesized by the ceramic method, only the Fe2B, Mo3+B, Mo4+B and Fe2+A oxidations have been observed. In these both cases, a quantitative analysis based on the discrepancy in reactivity of these different oxidizable cations has been used to determine the distribution of cations between the sublattices. As a result of the oxidation of all the oxidizable cations, the molybdenum defect ferrites may have a very high number of vacancies. These may reach 0.71 for x=0.5. The possibility to oxidize the Fe2+B and Mo3+B ions selectively, permits on the one hand to confirm the desummations of the DTG curves, and on the other hand to study the oxidation kinetics of these two ions. It has been also possible to show that the profile of the experimental DTG peaks obtained after desummation is comparable to the DTG peaks calculated from the isothermal kinetic parameters. Finally, the study of the cationic distribution of the oxidized phases has shown that the Mo6+ ions, initially in tetrahedral coordination can remain in octahedral site as the octahedral sites are also occupied by Fe2+ or Co2+ ions.

Published
1993

23. Correlation between Vibrational Spectrometry Behavior and Oxidation Mechanism of Molybdenum Substituted Magnetites

Author

Philippe Tailhades, L. Bouet, Bruno Domenichini, B. Gillot, and Abel Rousset

Subjects
chemistry.chemical_classification, Inorganic chemistry, Spinel, chemistry.chemical_element, Infrared spectroscopy, engineering.material, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Ion, Inorganic Chemistry, Crystallography, chemistry, Molybdenum, Vacancy defect, Materials Chemistry, Ceramics and Composites, engineering, Physical and Theoretical Chemistry, Spectroscopy, Inorganic compound, Solid solution
Abstract

The oxidation behavior of molybdenum substituted magnetites, Fe3-xMoxO4, has been investigated by Fourier transform infrared transmission. When the oxidation of Fe2+, Mo3+, and Mo4+ ions is achieved below 530°C, optical spectroscopy confirms the formation of cation-deficient spinels with a vacancy and cation ordering that depends on both oxidation and molybdenum content. The intense band at 840 cm-1 observed for cation-deficient spinels, as well as for transformation products, and the disappearance of the band at 726 cm-1 for initial samples prove that M06+ ions are present at tetrahedral sites of the spinel lattice. However, under certain thermal treatments, the Mo6+ ions remain in octahedral sites, namely when the octahedral sites are also occupied by Fe2+ ions.

Published
1993

24. Cationic distribution and oxidation kinetics of trivalent molybdenum ions in submicron molybdenum substituted magnetites

Author

Abel Rousset, L. Bouet, Philippe Tailhades, Bruno Domenichini, Bernard Gillot, and Pascal Perriat

Subjects
chemistry.chemical_classification, Valence (chemistry), Chemistry, Spinel, Inorganic chemistry, Cationic polymerization, Infrared spectroscopy, chemistry.chemical_element, General Chemistry, engineering.material, Condensed Matter Physics, Thermogravimetry, Molybdenum, engineering, General Materials Science, Qualitative inorganic analysis, Inorganic compound
Abstract

Valence states of molybdenum and iron ions and their cationic distribution on both octahedral (B) and tetrahedral (A) sites on the spinel structure of submicron molybdenum-substituted magnetites which are oxidized in cation deficient spinels have been performed by derivative thermogravimetry, IR spectroscopy and XPS. It was demonstrated that Fe 2+ B , Mo 3+ B , Mo 4+ B , Fe 2+ A and Mo 4+ A are successively oxidized into Fe 3+ and Mo 6+ ions below 450°C. A quantitative analysis based on this difference of reactivity of iron and molybdenum in relation to occupied sites (A or B) permits us to propose a cationic distribution for initial and oxidized phases. Kinetic studies of the oxidation process of Mo 3+ ions suggest that oxidation proceeds by way of a diffusion-controlled reaction in a cation deficient phase of variable composition with a chemical diffusion coefficient dependent on the vacancy content.

Published
1992

25. Controlling garnet film composition by magnetic-field-controlled radio frequency magnetron sputtering

Author

L. Bouet, C. Baubet, Hiroshi Yoshikawa, Philippe Tailhades, S. Hirono, C. Despax, Lionel Presmanes, Takaya Tanabe, A. Furuya, Abel Rousset, and M. Yamamoto

Subjects
Materials science, business.industry, General Physics and Astronomy, Sputter deposition, Cathode, Magnetic field, law.invention, Sputtering, law, Optoelectronics, High-power impulse magnetron sputtering, Radio frequency magnetron sputtering, business, Stoichiometry
Abstract

To find a way to control the compositional change in Bi-substituted garnet during sputtering, we studied the effects of controlling the cathode magnetic field. The magnetic-field-controlled rf magnetron sputtering method that we developed can create a garnet film whose composition is the same as that of the sputtering target. When we deposited a film of Bi-substituted Dy iron garnet–ferrite (Bi2DyFe4GaO12) by this method, there was no compositional change between the target and the film even after a long sputtering process. Therefore, this sputtering method is effective at suppressing compositional change during the film formation process.

Published
2000

26. Magneto-optical properties of a sputtered Bi-substituted Dy–Fe garnet-ferrite/hematite bilayer

Author

C. Despax, Lionel Presmanes, A. Furuya, Abel Rousset, Philippe Tailhades, Hiroshi Yoshikawa, Takaya Tanabe, L. Bouet, and M. Yamamoto

Subjects
Materials science, Bilayer, Metallurgy, Spinel, General Physics and Astronomy, Corundum, Hematite, engineering.material, Magneto optical, Chemical engineering, visual_art, visual_art.visual_art_medium, engineering, Ferrite (magnet), Rapid thermal annealing, Quartz
Abstract

Rapid thermal annealing was performed after a Bismuth-substituted Dy iron garnet-ferrite (Bi2DyFe4GaO12) was deposited on a quartz glass substrate having a hematite underlayer, and the effect of the hematite underlayer on the magneto-optical characteristics of the garnet ferrite film was evaluated. The presence of the underlayer greatly improved the magneto-optical effect of the garnet film, but the amount of improvement depended on the hematite phase. Big improvement was obtained using underlayer phases that are easily crystallized, i.e., Fe3O4 and γ-Fe2O3 which have a spinel structure, but not with α-Fe2O3 which has a corundum structure.

Published
1999

27. CoMn cation-deficient ferrite thin films: Interesting ways to tailor their magneto-optical properties

Author

L. Bouet, Philippe Tailhades, and Abel Rousset

Subjects
Diffraction, Materials science, business.industry, Coercivity, Condensed Matter Physics, Redox, Electronic, Optical and Magnetic Materials, Stress (mechanics), symbols.namesake, Optics, Oxidation state, Faraday effect, symbols, Ferrite thin films, Thin film, Composite material, business
Abstract

Cation-deficient CoMn ferrites were prepared as thin films. Their magneto-optical properties were studied and correlated with the oxidation reactions occurring in the films. The coercivity and remanent Faraday rotation variations could be, in part, attributed to the development of mechanical stresses, which could be revealed by use of grazing-angle X-ray diffraction. Moreover, a directional order could be created in thin films by slow cooling from 350°C. The creation of this reversible phenomenon led to an increase in coercivity without detectable modification of the oxidation and stress states of the samples. Control of the oxidation state and the creation of a directional order allowed modification of the magneto-optical properties of the ferrite thin films over a wide range.

Published
1996

28. Charge tuning in [111] grown GaAs droplet quantum dots

Author

Gang Wang, Thierry Amand, Neul Ha, Kazuaki Sakoda, Takaaki Mano, Mikhail M. Glazov, Eougenious Ivchenko, Xavier Marie, Bernhard Urbaszek, Marta L. Vidal, L. Bouet, Mikhail V. Durnev, Takashi Kuroda, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), National Institute for Materials Science (NIMS), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Photonic entanglement, Photoluminescence, Materials science, Physics and Astronomy (miscellaneous), Exciton, FOS: Physical sciences, Charge fluctuations, 02 engineering and technology, 01 natural sciences, 7. Clean energy, Molecular physics, Condensed Matter::Materials Science, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Emission spectrum, 010306 general physics, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Condensed Matter - Mesoscale and Nanoscale Physics, Quantum dots, Condensed Matter::Other, Lasers, Micro-photoluminescence, Biasing, Leptons, Emission spectroscopy, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, 3. Good health, Semiconductors, Exchange interactions, Quantum dot, Excited state, Excitons, Electric potential, 0210 nano-technology, Ground state
Abstract

We demonstrate charge tuning in strain free GaAs/AlGaAs quantum dots (QDs) grown by droplet epitaxy on a GaAs(111)A substrate. Application of a bias voltage allows the controlled charging of the QDs from $-3|e|$ to $+2|e|$. The resulting changes in QD emission energy and exciton fine-structure are recorded in micro-photoluminescence experiments at T=4K. We uncover the existence of excited valence and conduction states, in addition to the s-shell-like ground state. We record a second series of emission lines about 25meV above the charged exciton emission coming from excited charged excitons. For these excited interband transitions a negative diamagnetic shift of large amplitude is uncovered in longitudinal magnetic fields., Comment: 5 pages, 3 figures

Published
2014

29. Fine Powders of Co-Mn Cation Deficient Spinel Ferrites for Magneto-Optical Pigments

Author

Abel Rousset, M. Durand, Philippe Tailhades, and L. Bouet

Subjects
010302 applied physics, Acicular, Materials science, Metallurgy, Spinel, Analytical chemistry, General Physics and Astronomy, engineering.material, Coercivity, 01 natural sciences, Remanence, [PHYS.HIST]Physics [physics]/Physics archives, 0103 physical sciences, engineering, Curie temperature, Ferrite (magnet), Crystallite, Particle size
Abstract

Very small particles of Co-Mn defect spinel ferrites with acicular and spherical shape were prepared. Their magnetic and magneto-optical properties were measured in function of their oxidation state and their size. It was shown that the coercivity of acicular (AP) and spherical (SP) particles with a mean crystallite size close to 20 nm, reached 3800 and 2950 Oe respectively. The SP coercivity decreases when the grains sizes become lower than 20 nm, but remains higher than 1000 Oe for particles having crystallites close to 10-15 nm. The Curie temperature decreases also sligthly when the grains are smaller than 20 nm, while the remanent Faraday rotation falls from 0.6 to 0 deg/µm when the crystallite size is reduced from 40 to 7-8 nm. The Co-Mn ferrite particles studied have interesting properties, even they have not, for now, all the required properties to be high performance pigments for magneto-optical recording.

Published
1997

31. Mixed valence states of iron and molybdenum ions in MoxFe3−xO4 magnetites and related cation deficient ferrites

Author

Ph. Tailhades, Abel Rousset, Bruno Domenichini, L. Bouet, and Bernard Gillot

Subjects
chemistry.chemical_classification, Valence (chemistry), Inorganic chemistry, Cationic polymerization, chemistry.chemical_element, General Chemistry, Coercivity, Condensed Matter Physics, Ion, chemistry.chemical_compound, chemistry, Molybdenum, General Materials Science, Inorganic compound, Magnetite, Solid solution
Abstract

From a quantitative DTG analysis of the reactivity of iron and molybdenum ions in relation to their lattice site, cationic distribution is proposed for submicronic molybdenum substituted magnetites. The high coercivity of these spinels is found to be related to the important amount of Fe 2+ ions.

Published
1992

32. Magneto-optical properties of a sputtered Bi-substituted Dy iron garnet-ferrite/spinel-ferrite bilayer

Author

Hiroshi Yoshikawa, Lionel Presmanes, C. Despax, Philippe Tailhades, Abel Rousset, L. Bouet, A. Furuya, Yamamoto Manabu, and T. Ohkubo

Subjects
Materials science, Bilayer, Spinel, Analytical chemistry, engineering.material, Sputter deposition, Condensed Matter Physics, Microstructure, Electronic, Optical and Magnetic Materials, symbols.namesake, Faraday effect, symbols, engineering, Ferrite (magnet), Thin film, Quartz
Abstract

Bi-substituted Dy iron garnet-ferrites, Bi 2 DyFe 4 GaO 12 , were prepared by RF magnetron sputtering on a spinel-ferrite underlayer on a quartz glass substrate. This study investigated the effect of the spinel underlayer, a mixed crystal of Fe 3 O 4 and γ-Fe 2 O 3 , on improving the magneto-optical properties. It was found that the presence of the spinel-ferrite underlayer increased the Faraday effect, compared to that of a garnet layer with no underlayer, for which the Faraday effect was almost non-existent. It is concluded that the high-temperature-treated spinel-ferrite underlayer enhanced the magneto-optical characteristics. This bilayer structure is therefore promising for magneto-optical recording media.

33. About the interesting properties of mixed-valence defect spinel ferrites for mass storage media

Author

Stéphane Lebrun, Isabelle Pasquet, Philippe Tailhades, Abel Rousset, Corine Bonningue, and L. Bouet

Subjects
Valence (chemistry), Materials science, Condensed matter physics, business.industry, Spinel, Coercivity, engineering.material, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Mass storage, Condensed Matter::Materials Science, symbols.namesake, Optics, Surface-area-to-volume ratio, Faraday effect, symbols, engineering, Condensed Matter::Strongly Correlated Electrons, Physics::Chemical Physics, Thin film, Magnetic force microscope, business
Abstract

When the spinel ferrites present a large surface/volume ratio (i.e when they are in the form of thin films or fine powders) they can be oxidized into mixed-valence defect ferrites. These original spinels have magnetic, magneto-optical and optical properties making them interesting materials for high density recording media.

34. Cation-deficient spinel ferrites: Application for high-density write-once optical recording

Author

Corine Bonningue, Stéphane Le Brun, Philippe Tailhades, Abel Rousset, L. Bouet, and Isabelle Pasquet

Subjects
Materials science, business.industry, Spinel, General Engineering, General Physics and Astronomy, Mineralogy, Corundum, engineering.material, Laser, law.invention, Wavelength, Write-once, law, Optical recording, engineering, Optoelectronics, Ferrite (magnet), Thin film, business
Abstract

Thin films of defect spinel ferrites can be used as write-once read-many media working with blue wavelengths. In fact, because these non-stoichiometric ferrites are metastable, they can be transformed into corundum phases at moderate temperatures by a laser spot. The transformed regions have different optical indices from the starting ferrite film, making the readout process possible. Recording density of about 5 bits/µm2 was demonstrated.

35. Giant enhancement of the optical second-harmonic emission of WSe(2) monolayers by laser excitation at exciton resonances.

Author

Wang G, Marie X, Gerber I, Amand T, Lagarde D, Bouet L, Vidal M, Balocchi A, and Urbaszek B

Abstract

We show that the light-matter interaction in monolayer WSe_{2} is strongly enhanced when the incoming electromagnetic wave is in resonance with the energy of the exciton states of strongly Coulomb bound electron-hole pairs below the electronic band gap. We perform second harmonic generation (SHG) spectroscopy as a function of laser energy and polarization at T=4  K. At the exciton resonance energies we record an enhancement by up to 3 orders of magnitude of the SHG efficiency, due to the unusual combination of electric dipole and magnetic dipole transitions. The energy and parity of the exciton states showing the strong resonance effects are identified in 1- and 2-photon photoluminescence excitation experiments, corroborated by first principles calculations. Targeting the identified exciton states in resonant 2-photon excitation allows us to maximize k-valley coherence and polarization.

Published
2015
Full Text
View/download PDF

36. Carrier and polarization dynamics in monolayer MoS2.

Author

Lagarde D, Bouet L, Marie X, Zhu CR, Liu BL, Amand T, Tan PH, and Urbaszek B

Abstract

In monolayer MoS2, optical transitions across the direct band gap are governed by chiral selection rules, allowing optical valley initialization. In time-resolved photoluminescence (PL) experiments, we find that both the polarization and emission dynamics do not change from 4 to 300 K within our time resolution. We measure a high polarization and show that under pulsed excitation the emission polarization significantly decreases with increasing laser power. We find a fast exciton emission decay time on the order of 4 ps. The absence of a clear PL polarization decay within our time resolution suggests that the initially injected polarization dominates the steady-state PL polarization. The observed decrease of the initial polarization with increasing pump photon energy hints at a possible ultrafast intervalley relaxation beyond the experimental ps time resolution. By compensating the temperature-induced change in band gap energy with the excitation laser energy, an emission polarization of 40% is recovered at 300 K, close to the maximum emission polarization for this sample at 4 K.

Published
2014
Full Text
View/download PDF

37. Nuclear magnetization in gallium arsenide quantum dots at zero magnetic field.

Author

Sallen G, Kunz S, Amand T, Bouet L, Kuroda T, Mano T, Paget D, Krebs O, Marie X, Sakoda K, and Urbaszek B

Abstract

Optical and electrical control of the nuclear spin system allows enhancing the sensitivity of NMR applications and spin-based information storage and processing. Dynamic nuclear polarization in semiconductors is commonly achieved in the presence of a stabilizing external magnetic field. Here we report efficient optical pumping of nuclear spins at zero magnetic field in strain-free GaAs quantum dots. The strong interaction of a single, optically injected electron spin with the nuclear spins acts as a stabilizing, effective magnetic field (Knight field) on the nuclei. We optically tune the Knight field amplitude and direction. In combination with a small transverse magnetic field, we are able to control the longitudinal and transverse components of the nuclear spin polarization in the absence of lattice strain--that is, in dots with strongly reduced static nuclear quadrupole effects, as reproduced by our model calculations.

Published
2014
Full Text
View/download PDF

38. Readout characteristics of a near-field optical probe as a data-storage readout device: submicrometer scan height and resolution.

Author

Yoshikawa H, Ohkubo T, Fukuzawa K, Bouet L, and Yamamoto M

Abstract

A photodiode-embedded near-field scanning microscope cantilever (photocantilever) was used to scan in a noncontact, constant-height mode at a range common in hard disk drives to examine its readout capabilities when mounted on a flying-slider head. The intensity ratios of spatial frequencies that compose the obtained near-field image were analyzed by use of the fast Fourier transform. A simplified model was developed as a guiding principle for estimating the readout characteristics of the near-field optical probe in the above-proximity scan-height range.

Published
1999
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results