We present spatially- and time-resolved photoluminescence experiments on polar GaN/AlGaN quantum well structures,showing exciton propagation distance of tens of micrometers from generation position and exciton radiative lifetimes oftens of microseconds. We study in detail the dynamics and range of their relaxation/diffusion along the growth plane, asa function of temperature.

We report on sub-Terahertz photoconductivity of bulk HgxCd1-xTe crystals withcomposition close to semiconductor-to-semimetal topological transition. Low magnetic fieldShubnikov-de Hass like oscillations were observed with a period which does not depend onthe incident frequency. Moreover, anomalous B-periodic oscillations were also observed athigher magnetic fields.

The evolution of surface water waves in finite depth under wind forcing is reduced to an antidissipative Korteweg–de Vries–Burgers equation. We exhibit its solitary wave solution. Antidissipation accelerates and increases the amplitude of the solitary wave and leads to blow-up and breaking. Blow-up occurs in finite time for infinitely large asymptotic space so it is a nonlinear, dispersive, and antidissipative equivalent of the linear instability which occurs for infinite time. Due to antidissipation two given arbitrary and adjacent planes of constant phases of the solitary wave acquire different velocities and accelerations inducing breaking. Soliton breaking occurs in finite space in a time prior to the blow-up. We show that the theoretical growth in amplitude and the time of breaking are both testable in an existing experimental facility.

The present work concerns cuspate spits: slightly symmetrical geomorphic features growing along the shoreline in shallow waters. We develop a new formulation for the dynamics of cuspate spits. Our approach relies on classical paradigms such as a conservation law to the shoreface scale and an explicit formula for alongshore sediment transport. We derive a non-linear diffusion equation and a fully explicit solution for the growth of cuspate spits. From this general expression, we found interesting applications to quantify shoreline dynamics in the presence of cuspate spits. In particular, we point out a simple method for the datation of a cuspate spit given a limited number of input parameters. Furthermore, we develop a method to quantify the mean alongshore diffusivity along a shoreline perturbed by well-defined cuspate spits of known sizes. Finally, we introduce a formal relationship between the geometric characteristics (amplitude, length) of cuspate spits, which reproduce the self-similarity of these geomorphic features.

We present the magnetoresistance (MR) of highly doped monolayer graphene layers grown by chemical vapor deposition on 6H-SiC. The magnetotransport studies are performed on a large temperature range, from T=1.7 K up to room temperature. The MR exhibits a maximum in the temperature range 120–240 K. The maximum is observed at intermediate magnetic fields (B=2–6 T), in between the weak localization and the Shubnikov-de Haas regimes. It results from the competition of two mechanisms. First, the low-field magnetoresistance increases continuously with T and has a purely classical origin. This positive MR is induced by thermal averaging and finds its physical origin in the energy dependence of the mobility around the Fermi energy. Second, the high-field negative MR originates from the electron-electron interaction (EEI). The transition from the diffusive to the ballistic regime is observed. The amplitude of the EEI correction points towards the coexistence of both long- and short-range disorder in these samples.

We present magnetotransport measurements on a high electron density AlGaN/GaN heterostructure with two subbands populated at $\tau$ = 1.6 K. The transport scattering times, $\tau_\text{tr}$ , of each subband are first derived at low magnetic field by taking into account the magneto-intersubband scattering term. Then the quantum scattering times, $\tau_\text{q}$, are extracted from independent Dingle plots, obtained at higher magnetic fields. All scattering times are studied as a function of the total electronic density, increased by the persistent photo-conductivity effect. A standard modelization, based on all common scattering mechanisms, reveals that the transport scattering time is governed by the short-range AlGaN/GaN interface roughness (IR) scattering, whereas the quantum scattering time is due to the smooth potential induced by remote ionized impurities (II) at the GaN surface. This intermediate situation of mixed disorder, where the $\tau_\text{tr}/\tau_\text{q}$ ratio is greater than one, does not indicate that the mobility is limited by Coulomb scattering. It is due to the unusual condition $\tau_\text{tr}^\text{II} >\!\!\!> \tau_\text{tr}^\text{IR} >\!\!\!> \tau_\text{q}^\text{II}$