Two-dimensional topological insulator edge state backscattering by dephasing

To understand the seemingly absent temperature dependence in the conductance of two-dimensional topological insulator edge states, we perform a numerical study which identifies the quantitative influence of the combined effect of dephasing and elastic scattering in charge puddles close to the edges. We show that this mechanism may be responsible for the experimental signatures in HgTe/CdTe quantum wells if the puddles in the samples are large and weakly coupled to the sample edges. We propose experiments on artificial puddles which allow to verify this hypothesis and to extract the real dephasing time scale using our predictions. In addition, we present a new method to include the effect of dephasing in wave-packet-time-evolution algorithms.Comment: 7 pages, 5 figure

A W3C szabványosítási törekvései

Az 1994-ben alapított World Wide Web Consortium (W3C) egy olyan szabványosítási testület, melynek ajánlásai meghatározzák a webtechnológiák fejlődési irányvonalait. Az előadás ismerteti a W3C küldetését, működési alapelveit, fő tevékenységi körét. Röviden bemutatja a a W3C-technológiákat és egymásra épülésüket, és egy munkacsoport működési sémájával, valamint az ajánláskidolgozás folyamatával szemlélteti a W3C tipikus munkamenetét. Áttekintést ad továbbá a 2002-ben a kelet-közép-európai térségben elsőként megnyitott W3C Magyar Iroda célkitűzéseiről, a W3C-technológiák és alapelvek megismertetése és népszerűsítése érdekében kifejtett tevékenységéről

A webes akadálymentesítés helyzete Magyarországon

Napjainkban egyre többet hallani a honlapok akadálymentesítéséről, mint igény egyre gyakrabban merül fel az állam, illetve a különböző rászorulókat tömörítő szervezetek részéről. Ennek ellenére nagyon kevés az akadálymentes honlap, az oktatási intézményekből továbbra is úgy kerülnek ki az informatikusok, hogy még csak lehetőségük sem volt megtanulni, mit is jelent egy akadálymentes honlap kialakítása. A hazai helyzet áttekintése egy jó kiindulópont ahhoz, hogy hogyan érdemes, illetve hogyan nem érdemes akadálymentes honlapot készíteni. Az előadásban a konkrét példákon keresztül mutatjuk be az akadálymentes honlapokkal szemben támasztott alapvető követelményeket, illetve a leggyakoribb hibákat

Weak localization in mesoscopic hole transport: Berry phases and classical correlations

We consider phase-coherent transport through ballistic and diffusive two-dimensional hole systems based on the Kohn-Luttinger Hamiltonian. We show that intrinsic heavy-hole light-hole coupling gives rise to clear-cut signatures of an associated Berry phase in the weak localization which renders the magneto-conductance profile distinctly different from electron transport. Non-universal classical correlations determine the strength of these Berry phase effects and the effective symmetry class, leading even to antilocalization-type features for circular quantum dots and Aharonov-Bohm rings in the absence of additional spin-orbit interaction. Our semiclassical predictions are quantitatively confirmed by numerical transport calculations

Introducing Thermodynamics-Informed Symbolic Regression -- A Tool for Thermodynamic Equations of State Development

Thermodynamic equations of state (EOS) are essential for many industries as well as in academia. Even leaving aside the expensive and extensive measurement campaigns required for the data acquisition, the development of EOS is an intensely time-consuming process, which does often still heavily rely on expert knowledge and iterative fine-tuning. To improve upon and accelerate the EOS development process, we introduce thermodynamics-informed symbolic regression (TiSR), a symbolic regression (SR) tool aimed at thermodynamic EOS modeling. TiSR is already a capable SR tool, which was used in the research of https://doi.org/10.1007/s10765-023-03197-z. It aims to combine an SR base with the extensions required to work with often strongly scattered experimental data, different residual pre- and post-processing options, and additional features required to consider thermodynamic EOS development. Although TiSR is not ready for end users yet, this paper is intended to report on its current state, showcase the progress, and discuss (distant and not so distant) future directions. TiSR is available at https://github.com/scoop-group/TiSR and can be cited as https://doi.org/10.5281/zenodo.8317547

Continuous Interaction Data Acquisition and Evaluation. A Process Applied within a Smart, Robot Inhabited Apartment

Richter V, Kummert F. Continuous Interaction Data Acquisition and Evaluation. A Process Applied within a Smart, Robot Inhabited Apartment. In: Companion of the 2018 ACM/IEEE International Conference on Human-Robot Interaction - HRI '18. New York: ACM Press; 2018: 217-218

Towards Addressee Recognition in Smart Robotic Environments An Evidence Based Approach

Richter V, Kummert F. Towards Addressee Recognition in Smart Robotic Environments An Evidence Based Approach. In: Proceedings of the 1st Workshop on Embodied Interaction with Smart Environments - EISE '16. New York, NY: Association for Computing Machinery (ACM); 2016: 1

Fabry-P\'erot interference in gapped bilayer graphene with broken anti-Klein tunneling

We report the experimental observation of Fabry-P\'erot (FP) interference in the conductance of a gate-defined cavity in a dual-gated bilayer graphene (BLG) device. The high quality of the BLG flake, combined with the device's electrical robustness provided by the encapsulation between two hexagonal boron nitride layers, allows us to observe ballistic phase-coherent transport through a $1${\mu}m-long cavity. We confirm the origin of the observed interference pattern by comparing to tight-binding calculations accounting for the gate-tunable bandgap. The good agreement between experiment and theory, free of tuning parameters, further verifies that a gap opens in our device. The gap is shown to destroy the perfect reflection for electrons traversing the barrier with normal incidence (anti-Klein tunneling). The broken anti-Klein tunneling implies that the Berry phase, which is found to vary with the gate voltages, is always involved in the FP oscillations regardless of the magnetic field, in sharp contrast with single-layer graphene.Comment: 5 pages, 4 figure

Towards a quantum time mirror for non-relativistic wave packets

We propose a method – a quantum time mirror (QTM) – for simulating a partial time-reversal of the free-space motion of a nonrelativistic quantum wave packet. The method is based on a short-time spatially-homogeneous perturbation to the wave packet dynamics, achieved by adding a nonlinear time-dependent term to the underlying Schroedinger equation. Numerical calculations, supporting our analytical considerations, demonstrate the effectiveness of the proposed QTM for generating a time-reversed echo image of initially localized matter-wave packets in one and two spatial dimensions. We also discuss possible experimental realizations of the proposed QTM

Bloch-Zener Oscillations in Graphene and Topological Insulators

We show that superlattices based on zero-gap semiconductors such as graphene and mercury telluride exhibit characteristic Bloch--Zener oscillations that emerge from the coherent superposition of Bloch oscillations and multiple Zener tunneling between the electron and hole branch. We demonstrate this mechanism by means of wave packet dynamics in various spatially periodically modulated nanoribbons subject to an external bias field. The associated Bloch frequencies exhibit a peculiar periodic bias dependence which we explain within a two-band model. Supported by extensive numerical transport calculations, we show that this effect gives rise to distinct current oscillations observable in the I-V characteristics of graphene and mercury telluride superlattices