Density inhomogeneities and Rashba spin-orbit coupling interplay in oxide interfaces

There is steadily increasing evidence that the two-dimensional electron gas (2DEG) formed at the interface of some insulating oxides like LaAlO3/SrTiO3 and LaTiO3/SrTiO3 is strongly inhomogeneous. The inhomogeneous distribution of electron density is accompanied by an inhomogeneous distribution of the (self-consistent) electric field confining the electrons at the interface. In turn this inhomogeneous transverse electric field induces an inhomogeneous Rashba spin-orbit coupling (RSOC). After an introductory summary on two mechanisms possibly giving rise to an electronic phase separation accounting for the above inhomogeneity,we introduce a phenomenological model to describe the density-dependent RSOC and its consequences. Besides being itself a possible source of inhomogeneity or charge-density waves, the density-dependent RSOC gives rise to interesting physical effects like the occurrence of inhomogeneous spin-current distributions and inhomogeneous quantum-Hall states with chiral "edge" states taking place in the bulk of the 2DEG. The inhomogeneous RSOC can also be exploited for spintronic devices since it can be used to produce a disorder-robust spin Hall effect.Comment: 13 pages, 15 figure

Efficient Support for Video Communications in Wireless Home Networks

This paper investigates the performance of video communications over wireless networks employing the recently proposed Time-Division Unbalanced Carrier Sense Multiple access (TDuCSMA) coordination function. TDuCSMA is fully IEEE 802.11 standard compliant but offers novel bandwidth management capabilities. In this work the peculiar characteristics of TDuCSMA are configured and exploited to maximize the performance of video communications in a realistic home networking scenario. Simulation results show significant performance improvements with respect to legacy IEEE 802.11 network. The video quality gains are up to 13 dB PSNR with 500 ms playout buffer, while the average delay of the video packets is much lower, for the same amount of video traffic offered to the network. These results significantly contribute to enhance the quality of experience of the users of the video communicatio

Hard sphere-like dynamics in a non hard sphere liquid

The collective dynamics of liquid Gallium close to the melting point has been studied using Inelastic X-ray Scattering to probe lengthscales smaller than the size of the first coordination shell. %(momentum transfers, $Q$, $>$15 nm$^{-1}$). Although the structural properties of this partially covalent liquid strongly deviate from a simple hard-sphere model, the dynamics, as reflected in the quasi-elastic scattering, are beautifully described within the framework of the extended heat mode approximation of Enskog's kinetic theory, analytically derived for a hard spheres system. The present work demonstrates the applicability of Enskog's theory to non hard- sphere and non simple liquids.Comment: 5 pages, 2 figures, accepted in Phys. Rev. Let

Evidence of short time dynamical correlations in simple liquids

We report a molecular dynamics (MD) study of the collective dynamics of a simple monatomic liquid -interacting through a two body potential that mimics that of lithium- across the liquid-glass transition. In the glassy phase we find evidences of a fast relaxation process similar to that recently found in Lennard-Jones glasses. The origin of this process is ascribed to the topological disorder, i.e. to the dephasing of the different momentum $Q$ Fourier components of the actual normal modes of vibration of the disordered structure. More important, we find that the fast relaxation persists in the liquid phase with almost no temperature dependence of its characteristic parameters (strength and relaxation time). We conclude, therefore, that in the liquid phase well above the melting point, at variance with the usual assumption of {\it un-correlated} binary collisions, the short time particles motion is strongly {\it correlated} and can be described via a normal mode expansion of the atomic dynamics.Comment: 7 pages, 7 .eps figs. To appear in Phys. Rev.

Time Driven Priority Router Implementation and First Experiments

This paper reports on the implementation of Time-Driven Priority (TDP) scheduling on a FreeBSD platform. This work is part of a TDP prototyping and demonstration project aimed at showing the implications of TDP deployment in packet-switched networks, especially benefits for real-time applications. This paper focuses on practical aspects related to the implementation of the technology on a Personal Computer (PC)-based router and presents the experimental results obtained on a testbed network. The basic building blocks of a TDP router are described and implementation choices are discussed. The relevant results achieved and here presented can be categorized into two types: qualitative results, including the successful integration of all needed blocks and the insight obtained on the complexity related to the implementation of a TDP router, and quantitative ones, including measures of achievable network utilization and of jitter experienced on a fully-loaded TDP network. The outcome demonstrates the effectiveness of the presented implementation while confirming TDP points of strengt

High frequency dynamics in a monatomic glass

The high frequency dynamics of glassy Selenium has been studied by Inelastic X-ray Scattering at beamline BL35XU (SPring-8). The high quality of the data allows one to pinpoint the existence of a dispersing acoustic mode for wavevectors ($Q$) of $1.5<Q<12.5$ nm$^{-1}$, helping to clarify a previous contradiction between experimental and numerical results. The sound velocity shows a positive dispersion, exceeding the hydrodynamic value by $\approx$ 10% at $Q<3.5$ nm$^{-1}$. The $Q^2$ dependence of the sound attenuation $\Gamma(Q)$, reported for other glasses, is found to be the low-$Q$ limit of a more general $\Gamma(Q) \propto \Omega(Q)^2$ law which applies also to the higher $Q$ region, where $\Omega(Q)\propto Q$ no longer holds.Comment: Phys. Rev. Lett. (Accepted

Phonon-like and single particle dynamics in liquid lithium

The dynamic structure factor, S(Q,E), of liquid lithium (T=475 K) has been determined by inelastic x-ray scattering (IXS) in the momentum transfer region (Q = 1.4-110 nm-1). These data allow to observe how, in a simple liquid, a phonon-like collective mode evolves towards the single particle dynamics. As a function of Q, one finds: i) at low Q's, a sound mode with a positive dispersion of the sound velocity, ii) at intermediate Q's, excitations whose energy oscillates similarly to phonons in the crystal Brillouin zones, and iii) at high Q's, the S(Q,E) approaches a Gaussian shape, indicating that the single particle dynamics has been reached.Comment: 3 pages and 5 figure

Joint Interactive Visualization of 3D Models and Pictures in Walkable Scenes

The 3D digitalization of buildings, urban scenes, and the like is now a mature technology. Highly complex, densely sampled, reasonably accurate 3D models can be obtained by range-scanners and even image-based reconstruction methods from dense image collections. Acquisition of naked geometry is not enough in Cultural Heritage applications, because the surface colors (e.g. pictorial data) are clearly of central importance. Moreover, the 3D geometry cannot be expected to be complete, lacking context, parts made of materials like glass and metal, difficult to reach surfaces, etc. Easily captured photographs are the natural source of the appearance data missing in the 3D geometry. In spite of the recent availability of reliable technologies to align 2D images on 3D data, the two sides of the dataset are not easy to combine satisfactorily in a visualization. Texture mapping techniques, perhaps the most obvious candidate for the task, assume strict content consistency (3D to 2D, and 2D to 2D) which these datasets do not and should not exhibit (the advantage of pictures consisting in their ability to feature details, lighting conditions, non-persistent items, etc. which are absent in the 3D models or in the other pictures). In this work, we present a simple but effective technique to jointly and interactively visualize 2D and 3D data of this kind. This technique is used within PhotoCloud [IV12], a flexible opensource tool which is being designed to browse, navigate, and visualize large, remotely stored 3D-2D datasets, and which emphasizes scalability, usability, and ability to cope with heterogeneous data from various sources

Collective dynamics of liquid aluminum probed by Inelastic X-ray Scattering

An inelastic X-ray scattering experiment has been performed in liquid aluminum with the purpose of studying the collective excitations at wavevectors below the first sharp diffraction peak. The high instrumental resolution (up to 1.5 meV) allows an accurate investigation of the dynamical processes in this liquid metal on the basis of a generalized hydrodynamics framework. The outcoming results confirm the presence of a viscosity relaxation scenario ruled by a two timescale mechanism, as recently found in liquid lithium.Comment: 8 pages, 7 figure