1,116 research outputs found
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 szabvĂĄnyosĂtĂĄsi törekvĂ©sei
Az 1994-ben alapĂtott World Wide Web Consortium (W3C) egy olyan szabvĂĄnyosĂtĂĄsi testĂŒlet, melynek ajĂĄnlĂĄsai meghatĂĄrozzĂĄk a webtechnolĂłgiĂĄk fejlĆdĂ©si irĂĄnyvonalait.
Az elĆadĂĄs ismerteti a W3C kĂŒldetĂ©sĂ©t, mƱködĂ©si alapelveit, fĆ tevĂ©kenysĂ©gi körĂ©t. Röviden bemutatja a a W3C-technolĂłgiĂĄkat Ă©s egymĂĄsra Ă©pĂŒlĂ©sĂŒket, Ă©s egy munkacsoport mƱködĂ©si sĂ©mĂĄjĂĄval, valamint az ajĂĄnlĂĄskidolgozĂĄs folyamatĂĄval szemlĂ©lteti a W3C tipikus munkamenetĂ©t.
ĂttekintĂ©st ad tovĂĄbbĂĄ a 2002-ben a kelet-közĂ©p-eurĂłpai tĂ©rsĂ©gben elsĆkĂ©nt megnyitott W3C Magyar Iroda cĂ©lkitƱzĂ©seirĆl, a W3C-technolĂłgiĂĄk Ă©s alapelvek megismertetĂ©se Ă©s nĂ©pszerƱsĂtĂ©se Ă©rdekĂ©ben kifejtett tevĂ©kenysĂ©gĂ©rĆl
A webes akadĂĄlymentesĂtĂ©s helyzete MagyarorszĂĄgon
Napjainkban egyre többet hallani a honlapok akadĂĄlymentesĂtĂ©sĂ©rĆl, mint igĂ©ny egyre gyakrabban merĂŒl fel az ĂĄllam, illetve a kĂŒlönbözĆ rĂĄszorulĂłkat tömörĂtĆ szervezetek rĂ©szĂ©rĆl. Ennek ellenĂ©re nagyon kevĂ©s az akadĂĄlymentes honlap, az oktatĂĄsi intĂ©zmĂ©nyekbĆl tovĂĄbbra is Ășgy kerĂŒlnek ki az informatikusok, hogy mĂ©g csak lehetĆsĂ©gĂŒk sem volt megtanulni, mit is jelent egy akadĂĄlymentes honlap kialakĂtĂĄsa.
A hazai helyzet ĂĄttekintĂ©se egy jĂł kiindulĂłpont ahhoz, hogy hogyan Ă©rdemes, illetve hogyan nem Ă©rdemes akadĂĄlymentes honlapot kĂ©szĂteni. Az elĆadĂĄsban a konkrĂ©t pĂ©ldĂĄkon keresztĂŒl mutatjuk be az akadĂĄlymentes honlapokkal szemben tĂĄmasztott alapvetĆ követelmĂ©nyeket, illetve a leggyakoribb hibĂĄkat
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 {\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 â a quantum time mirror (QTM) â 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
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