arXiv subjects

Manuel Meyer

Publications and source records attributed to Manuel Meyer.

At least 19 recordsLinked to original sources

arXiv2026

Electrostatic Control Enables Robust Helical Edge Channel Transport in III-V Quantum Spin Hall Insulators

Quantum spin Hall transport in InAs/GaInSb-based two-dimensional topological insulators can be limited by parasitic bulk and edge contributions. We demonstrate that these limitations are effectively mitigated through electrostatic control in dual-gated InAs/GaInSb/InAs trilayer quantum wells grown on AlSb quasi-substrates. In macroscopic Hall bars exceeding the phase coherence length, a multi-probe analysis reveals an insulating bulk and a constant edge resistance over a wide electric-field range. In microscopic devices with edge lengths below the phase coherence lengths, the edge resistance remains robust and quantized accross a broad field range, revealing the intrinsic resilience of helical edge channels to electric-field perturbations. Only beyond a threshold value, parasitic edge contributions emerge. These results establish dual gating as a reliable strategy to suppress parasitic conduction while stabilizing helical edge transport, providing a versatile and reproducible platform for tunable topological transport in III-V quantum spin Hall systems.

cond-mat.mes-hall↗

arXiv2026

Towards Autonomous Railway Operations: A Semi-Hierarchical Deep Reinforcement Learning Approach to the Vehicle Rescheduling Problem

Managing disruptions in railway traffic management is a major challenge. Rising traffic density and infrastructure limits increase complexity, making the Vehicle Routing and Scheduling Problem (VRSP) difficult to solve reliably and in real time. While Operational Research (OR) methods are widely used, most dispatching still relies on human expertise due to the problem's exponential combinatorial complexity. Reinforcement Learning (RL) has gained attention for its potential in multi-agent coordination, but existing RL approaches often underperform OR methods and struggle to scale in dense rail networks. This paper addresses this gap from a machine learning perspective by introducing a semi-hierarchical RL formulation tailored to operational railway constraints. The method separates dispatching from routing through dedicated action and observation spaces, enabling policies to specialise in distinct decision scopes and addressing the imbalance between rare dispatch decisions and frequent routing updates. The approach is evaluated on the Flatland-RL simulator across five difficulty levels and 50 random seeds, with 7 to 80 trains. Results show substantially improved coordination, resource utilisation, and robustness compared with heuristic baselines and monolithic RL, nearly doubling the number of trains reaching their destinations, while keeping deadlock rates below 5% and adaptively sequencing, delaying, or cancelling trains under heavy congestion.

cs.AI↗

arXiv2026

Characterization of a Two-Channel Optical and Near-infrared Transition Edge Sensor System for Rare-Event Searches

Transition edge sensors (TESs) are superconducting energy-resolving microcalorimeters that have demonstrated low background rates as well as quantum efficiencies close to unity for photons at optical and near-infrared wavelengths. This makes these detectors well suited for rare-event searches. We report on the comprehensive characterization of a two-channel detector module consisting of two tungsten TESs optimized for the detection of photons with a wavelength of 1064nm. The devices achieve a system detection efficiency of $(86\pm1)$%, an energy resolution better than 7%, and a background dark-count rate of photon-like events below 6mHz when coupled to an optical fiber. Using an unbinned likelihood framework, we find the dark count rate to be compatible with blackbody radiation from the room-temperature laboratory environment. Thanks to the energy resolution of the TESs, we show that it is possible to detect monochromatic signals at 1064nm with photon rates $\geqslant 2.7_{-0.6}^{+0.8} \times10^{-5}$Hz, which corresponds to a power of $\geqslant(5.0_{-1.1}^{+1.4})\times10^{-24}$W, within 20 days of measurement time at the 5$\sigma$ confidence level. This makes our detectors well suited for searches for hypothetical axions and axion-like particles with experiments such as the Any Light Particle Search II (ALPS II) or axion interferometers. The developed methodologies are not only applicable to axion searches, but are also relevant for rare-event searches with TESs in general.

physics.ins-det↗

arXiv2025

Any Light Particle Searches with ALPS II: first science results

The light-shining-through-a-wall experiment ALPS II at DESY in Hamburg searched for axions and similar lightweight particles in its first science campaign from February to May 2024. No evidence for the existence of such particles was found. For pseudoscalar bosons like the axion, with masses below about 0.1 meV, we achieved a limit for the di-photon coupling strength of 1.5e-9 1/GeV at a 95% confidence level. This is more than a factor of 20 improvement compared to all previous similar experiments. We also provide limits on photon interactions for scalar, vector and tensor bosons. An achievement of this first science campaign is the demonstration of stable operation and robust calibration of the complex experiment. Currently, the optical system of ALPS II is being upgraded aiming for another two orders of magnitude sensitivity increase.

hep-ex↗

arXiv2025

Constraints on the intergalactic magnetic field from Fermi-LAT observations of GRB 221009A

A cosmological origin of the magnetic fields in large scale structures of the Universe would require a non-negligible magnetic field in cosmic voids, which, however, remains undetected. Gamma-ray emission from gamma-ray bursts (GRBs) offers the opportunity to indirectly probe such an intergalactic magnetic field (IGMF), as gamma rays interact with cosmic radiation fields, producing electron-positron pairs, and initiate an electromagnetic cascade. The deflection of the pairs in the IGMF results in a time-delayed signal at GeV energies. Using observations with the Fermi Large Area Telescope of the GRB 221009A, we are able to derive the most stringent constraints to date from the non-observation of the cascade and rule out magnetic fields B < 2.5 x 10^{-17} G at 95% confidence level for a coherence length larger than 1 Mpc. Our results are comparable to limits obtained from blazar observations but do not suffer from assumptions on the duty cycle of the gamma-ray source or whether inverse-Compton scattering losses dominate over the development of plasma instabilities.

astro-ph.HE↗

arXiv2025

A topological field-effect memristor

Overcoming the limitations of the von Neumann architecture requires new computational paradigms capable of solving complex problems efficiently. Quantum and neuromorphic computing rely on unconventional materials and device functionalities, yet achieving resilience to imperfections and reliable operation remains a major challenge. This has motivated growing interest in topological materials that provide robust and low-power operation while preserving coherence. However, integrating coherent topological transport with non-volatile memory functionality in a single reconfigurable device has remained challenging. In this work, we demonstrate a topological field-effect memristor based on inverted InAs/GaInSb/InAs trilayer quantum wells operating in the quantum spin Hall regime. The intrinsic floating-gate behavior allows one to reconfigure the transistor functionality into memristive functionality with broad electric-field tunability. Unlike other memristor implementations, one resistance state is governed entirely by dissipationless, coherent transport through helical edge channels, while the other arises from incoherent bulk conduction. By combining electrically tunable coherent and incoherent transport with memory functionality, our device realizes a prototypical topological electronic element that integrates coherent transport and adaptive memristive behavior, paving the way for hybrid quantum-neuromorphic architectures.

cond-mat.mes-hall↗

arXiv2025

Niebla: an open-source code for modeling the extragalactic background light

The flux of extragalactic gamma rays is attenuated through interactions with optical and infrared photons of the extragalactic background light (EBL). The EBL is an isotropic, diffuse photon field that is difficult to measure directly at these wavelengths due to strong foreground emission. We present niebla, the first open-source code to compute the EBL from optical to far-infrared wavelengths using a phenomenological approach that accepts fully customizable inputs. This software enables a detailed modeling of the influence of EBL optical depth on gamma-ray observations and facilitates the distinction between different dust reemission models. The code models the optical background primarily from stellar emission, by evolving the spectrum of a single stellar population as a function of redshift, considering mean metallicity evolution and star formation rate density. Additional sources to the EBL can be provided by the user. The code already includes optional contributions from, e.g., stripped stars, intra-halo light, or the decay of axion dark matter. The optical emissivity is then absorbed by interstellar dust and reemitted in the infrared regime. We provide multiple prescriptions to model this process, using spectral dust templates or a combination of blackbodies. We provide three EBL models calculated with different dust reemission prescriptions, which have been fitted to various observational data sets. In addition, we showcase the versatility of our model through a simulated observation of the blazar Markarian 501 in a high-flux state with the LHAASO array. We find that the simulated VHE spectrum is highly sensitive to the photon density of the EBL at infrared wavelengths. Our model will therefore allow the community to distinguish between different dust reemission models and constrain EBL parameters with future observations.

astro-ph.CO↗

arXiv2025

Quantum spin Hall effect in III-V semiconductors at elevated temperatures: advancing topological electronics

The quantum spin Hall effect (QSHE), a hallmark of topological insulators, enables dissipationless, spin-polarized edge transport and has been predicted in various two-dimensional materials. However, challenges such as limited scalability, low-temperature operation, and the lack of robust electronic transport have hindered practical implementations. Here, we demonstrate the QSHE in an InAs/GaInSb/InAs trilayer quantum well structure operating at elevated temperatures. This platform meets key criteria for device integration, including scalability, reproducibility, and tunability via electric field. When the Fermi level is positioned within the energy gap, we observe quantized resistance values independent of device length and in both local and nonlocal measurement configurations, confirming the QSHE. Helical edge transport remains stable up to T = 60 K, with further potential for higher-temperature operation. Our findings establish the InAs/GaInSb system as a promising candidate for integration into next-generation devices harnessing topological functionalities, advancing the development of topological electronics.

cond-mat.mes-hall↗

arXiv2025

Unveiling the Quantum Nature of Black Holes: Towards a Proof of Hawking Radiation through Gamma-Ray Observations

Hawking's groundbreaking prediction that black holes emit thermal radiation and ultimately evaporate remains unverified due to the extreme faintness of this radiation for stellar-mass or larger black holes. In this study, we explore a novel observational strategy to search for Hawking radiation from asteroid-mass black hole morsels -- hypothetical small black holes that may form and be ejected during catastrophic events such as binary black hole mergers. These black hole morsels are expected to emit gamma rays in the GeV-TeV range on observable timescales. We analyze data from the Fermi Large Area Telescope coinciding with the well-localized binary black hole merger GW170814, searching for delayed gamma-ray signatures associated with morsel evaporation. While we find no evidence for such emission, we place exclusion limits on morsel masses, ruling out the 4 x 10^8 kg scenario at the 95 percent confidence level for a total emitted mass of one solar mass. We also outline future directions, including the incorporation of late-time evaporation spikes, systematic application across the growing gravitational wave catalog, and the enhanced discovery potential of next-generation facilities such as the Cherenkov Telescope Array Observatory.

astro-ph.HE↗

arXiv2025

Binary Classification of Light and Dark Time Traces of a Transition Edge Sensor Using Convolutional Neural Networks

The Any Light Particle Search II (ALPS II) is a light shining through a wall experiment probing the existence of axions and axion-like particles using a 1064 nm laser source. While ALPS II is already taking data using a heterodyne based detection scheme, cryogenic transition edge sensor (TES) based single-photon detectors are planned to expand the detection system for cross-checking the potential signals, for which a sensitivity on the order of $10^{-24}$ W is required. In order to reach this goal, we have investigated the use of convolutional neural networks (CNN) as binary classifiers to distinguish the experimentally measured 1064 nm photon triggered (light) pulses from background (dark) pulses. Despite extensive hyperparameter optimization, the CNN based binary classifier did not outperform our previously optimized cut-based analysis in terms of detection significance. This suggests that the used approach is not generally suitable for background suppression and improving the energy resolution of the TES. We partly attribute this to the training confusion induced by near-1064 nm black-body photon triggers in the background, which we identified as the limiting background source as concluded in our previous works. However, we argue that the problem ultimately lies in the binary classification based approach and believe that regression models would be better suitable for addressing the energy resolution. Unsupervised machine learning models, in particular neural network based autoencoders, should also be considered potential candidates for the suppression of noise in time traces. While the presented results and associated conclusions are obtained for TES designed to be used in the ALPS II experiment, they should hold equivalently well for any device whose output signal can be considered as a univariate time trace.

physics.ins-det↗

arXiv2025

How can a geothermal storage system be optimally integrated into a local district? A case study

Achieving net-zero targets requires the phase-out of fossil-based heating. A major challenge is the seasonal mismatch between renewable heat supply and demand. District heating networks often dispose of excess heat in summer and rely on fossil backups in winter. Large-scale thermal energy storage offers a solution by storing surplus summer heat for use during winter, thus reducing the need for fossil fuels. This study investigates the feasibility of a large-scale thermal storage system at a power production site that supplies a large district heating network in the city of Bern, Switzerland. Specifically, the study examines the potential of a geothermal storage system to offset fossil fuel heat generation in winter by utilising heat stored during the summer months. Using a Python-based multi-energy system model, we simulate the optimal operation of the geothermal storage system with respect to cost and emissions, considering both supply and demand on an hourly basis over one year. Multi-objective optimisation is applied to generate a Pareto-optimal front. The results show that the geothermal storage system eliminates the requirement of 8 GWh of gas-powered heat supply and increases the waste heat utilisation by 20%, therefore lowering emissions. This effect is further increased when combined with an expansion of the district heating network, as individual, emission-heavy heaters are replaced by low-emission heat from the district heating network. The findings presented in this study can prove useful when evaluating similar systems across Switzerland.

eess.SY↗

arXiv2025

First direct search for light dark matter interactions in a transition-edge sensor

We propose the use of transition-edge sensor (TES) single-photon detectors as a simultaneous target and sensor for direct dark matter searches, and report results from the first search of this kind. We perform a 489 h science run with a TES device optimized for the detection of 1064 nm photons, with a mass of ~0.2 ng and an energy threshold of ~0.3 eV, and set new limits on dark matter interactions with both electrons and nucleons for dark matter with mass below the MeV scale. With their excellent energy resolution, TESs enable search strategies that are complementary to recent results from superconducting nanowire single-photon detectors and kinetic inductance detectors. We show that next-generation TES arrays hold promise to probe new regions of light dark matter parameter space.

physics.ins-det↗

arXiv2025

Sensitivity of a Gigahertz Fabry-P\'erot Resonator for Axion Dark Matter Detection

Axions are hypothetical pseudo-Nambu Goldstone bosons that could explain the observed cold dark matter density and solve the strong CP problem of quantum chromodynamics (QCD). Haloscope experiments commonly employ resonant cavities to search for a conversion of axion dark matter into photons in external magnetic fields. As the expected signal power degrades with increasing frequency, this approach becomes challenging at frequencies beyond tens of Gigahertz. Here, we propose a novel haloscope design based on an open Fabry-P\'erot resonator. Operating a small-scale resonator at cryogenic temperatures and at modest magnetic fields should already lead to an unparalleled sensitivity for photon-axion couplings $g_{a\gamma} \gtrsim 3\times10^{-12}\,\mathrm{GeV}^{-1}$ at 35GHz. We demonstrate how this sensitivity could be further improved using graded-phase mirrors and sketch possibilities to probe benchmark models of the QCD axion.

physics.ins-det↗

arXiv2025

Simulation and measurement of Black Body Radiation background in a Transition Edge Sensor

The Any Light Particle Search II (ALPS II) experiment at DESY, Hamburg, is a Light-Shining-through-a-Wall (LSW) experiment aiming to probe the existence of axions and axion-like particles (ALPs), which are candidates for dark matter. Data collection in ALPS II is underway utilizing a heterodyne-based detection scheme. A complementary run for confirmation or as an alternative method is planned using single photon detection, requiring a sensor capable of measuring low-energy photons ($1064\,\mathrm{nm}$, $1.165\,\mathrm{eV}$) with high efficiency (higher than $50\,\%$) and a low background rate (below $7.7\cdot10^{-6}\,\mathrm{cps}$). To meet these requirements, we are investigating a tungsten Transition Edge Sensor (TES) provided by NIST, which operates in its superconducting transition region at millikelvin temperatures. This sensor exploits the drastic change in resistance caused by the absorption of a single photon. We find that the background observed in the setup with a fiber-coupled TES is consistent with Black Body Radiation (BBR) as the primary background contributor. A framework was developed to simulate BBR propagation to the TES under realistic conditions. The framework not only allows the exploration of background reduction strategies, such as improving the TES energy resolution, but also reproduces, within uncertainties, the spectral distribution of the observed background. These simulations have been validated with experimental data, in agreement with the modeled background distribution, and show that the improved energy resolution reduces the background rate in the $1064\,\mathrm{nm}$ signal region by one order of magnitude, to approximately $10^{-4}\,\mathrm{cps}$. However, this rate must be reduced further to meet the ALPS II requirements.

hep-ex↗

arXiv2025

A Conceptual Framework for AI-based Decision Systems in Critical Infrastructures

The interaction between humans and AI in safety-critical systems presents a unique set of challenges that remain partially addressed by existing frameworks. These challenges stem from the complex interplay of requirements for transparency, trust, and explainability, coupled with the necessity for robust and safe decision-making. A framework that holistically integrates human and AI capabilities while addressing these concerns is notably required, bridging the critical gaps in designing, deploying, and maintaining safe and effective systems. This paper proposes a holistic conceptual framework for critical infrastructures by adopting an interdisciplinary approach. It integrates traditionally distinct fields such as mathematics, decision theory, computer science, philosophy, psychology, and cognitive engineering and draws on specialized engineering domains, particularly energy, mobility, and aeronautics. Its flexibility is further demonstrated through a case study on power grid management.

cs.CY↗

arXiv2024

Simulations for direct dark matter searches using ALPS II's TES detection system

Transition Edge Sensors (TES) are superconducting microcalorimeters that can be used for single-photon detection with extremely low backgrounds. When they are within their superconducting transition region, small temperature fluctuations - like the energy deposited by single photons - lead to large resistance variations. These variations can be measured using Superconducting Quantum Interference Devices (SQUIDs). This technology is planned to be used as a single-photon detector for later runs of the ALPS II experiment, a light-shining-through-walls experiment at DESY Hamburg, searching for Axion-Like Particles (ALPs), which are possible Dark Matter (DM) candidates. Due to the very low dark count rates in our setup, our TES system might be viable for direct DM searches at sub-MeV masses through electron-scattering of DM in the superconducting chip, as well. Simulations concerning background rejection and calibration methods demonstrate the needed sub-eV sensitivity already.

hep-ex↗

arXiv2024

Coexistence of Topological and Normal Insulating Phases in Electro-Optically Tuned InAs/GaSb Bilayer Quantum Wells

We report on the coexistence of both normal and topological insulating phases in InAs/GaSb bilayer quantum well induced by the built-in electric field tuned optically and electrically. The emergence of topological and normal insulating phases is assessed based on the evolution of the charge carrier densities, the resistivity dependence of the gap via in-plane magnetic fields and the thermal activation of carriers. For the Hall bar device tuned optically, we observe the fingerprints associated with the presence of only the topological insulating phase. For another Hall bar processed identically but with an additional top gate, the coexistence of normal and topological insulating phases is found by electrical tuning. Our finding paves the way for utilizing a new electro-optical tuning scheme to manipulate InAs/GaSb bilayer quantum wells to obtain trivial-topological insulating interfaces in the bulk rather than at the physical edge of the device.

cond-mat.mes-hall↗

arXiv2023

Constraints on axionlike particles from a combined analysis of three flaring $\textit{Fermi}$ flat-spectrum radio quasars

Many theories beyond the Standard Model of particle physics predict the existence of axionlike particles (ALPs) that mix with photons in the presence of a magnetic field. Searching for the effects of ALP-photon mixing in gamma-ray observations of blazars has provided some of the strongest constraints on ALP parameter space so far. Previously, only individual sources have been analysed. We perform a combined analysis on $\textit{Fermi}$ Large Area Telescope data of three bright, flaring flat-spectrum radio quasars, with the blazar jets themselves as the dominant mixing region. For the first time, we include a full treatment of photon-photon dispersion within the jet, and account for the uncertainty in our B-field model by leaving the field strength free in the fitting. Overall, we find no evidence for ALPs, but are able to exclude the ALP parameters $m_a\lesssim200$ neV and $g_{aγ}\gtrsim 5 \times 10^{-12}$ GeV$^{-1}$ with 95\% confidence.

astro-ph.HE↗