Ref HAL: hal-01697455_v1
DOI: 10.1063/1.5019629
WoS: 000424053600017
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6 Citations
Résumé:

The elastic constants of high-quality, single-crystal hexagonal boron nitride (h-BN) have been measured by means of high resolution Brillouin spectroscopy using a modified reflected light microscope. The sound propagation velocity in the c-axis direction and perpendicular to the c-axis have been obtained from the Brillouin frequency shift, with a proper account taken of the vast difference between the ordinary and extraordinary refractive indices recently reported in the highly anisotropic layered h-BN crystal. The elastic constants c11 and c33 obtained from the Brillouin experiments are somewhat lower than previous determinations based on inelastic x-ray measurements and confirm the overestimation of the h-BN elastic constants by ab initio calculations based on density functional perturbation theory in the local density approximation.

Ref HAL: hal-01690614_v1
DOI: 10.1103/PhysRevB.97.035423
WoS: 000423118900005
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14 Citations
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Radiative heat transport mediated by near-field interactions is known to be superdiffusive in dilute, many-body systems. Here we use a generalized Landauer theory of radiative heat transfer in many-body planar systems to demonstrate a nonmonotonic transition from superdiffusive to ballistic transport in dense systems. We show that such a transition is associated to a change of the polarization of dominant modes. Our findings are complemented by a quantitative study of the relaxation dynamics of the system in the different regimes of heat transport. This result could have important consequences on thermal management at nanoscale of many-body systems.

Ref HAL: hal-01691523_v1
DOI: 10.1111/jmi.12657
WoS: 000415900300012
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1 Citation
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In this work, we analyse the microstructure and local chemical composition of green-emitting InxGa1-xN/GaN quantum well (QW) heterostructures in correlation with their emission properties. Two samples of high structural quality grown by metalorganic vapour phase epitaxy (MOVPE) with a nominal composition of x = 0.15 and 0.18 indium are discussed. The local indium composition is quantitatively evaluated by comparing scanning transmission electron microscopy (STEM) images to simulations and the local indium concentration is extracted from intensity measurements. The calculations point out that the measured indium fluctuations may be correlated to the large width and intensity decrease of the PL emission peak.

Ref HAL: hal-01932599_v1
Ref Arxiv: 1712.10312
DOI: 10.1103/PhysRevB.97.165419
WoS: 000430058200006
Ref. & Cit.: NASA ADS
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9 Citations
Résumé:

We discuss neutral and charged complexes (biexciton and trion) formed by indirect excitons in layered quasi-two-dimensional semiconductor heterostructures. Indirect excitons -- long-lived neutral Coulomb-bound pairs of electrons and holes of different layers -- have been known for semiconductor coupled quantum wells and are recently reported for van der Waals heterostructures such as bilayer graphene and transition metal dichalcogenides. Using the configuration space approach, we derive the analytical expressions for the trion and biexciton binding energies as functions of the interlayer distance. The method captures essential kinematics of complex formation to reveal significant binding energies, up to a few tens of meV for typical interlayer distances ~3-5 A, with the trion binding energy always being greater than that of the biexciton. Our results can contribute to the understanding of more complex many-body phenomena such as exciton Bose-Einstein condensation and Wigner-like electron-hole crystallization in layered semiconductor heterostructures.

Commentaires: 10 pages, 4 figures, 105 references. arXiv admin note: text overlap with arXiv:1605.02348. Réf Journal: Phys. Rev. B 97, 165419 (2018)