arXiv subjects

Davide Costanzo

Publications and source records attributed to Davide Costanzo.

10 recordsLinked to original sources

arXiv2025

JENA Computing Initiative WP2 Report: Software and Heterogeneous Architectures

The scientific communities of nuclear, particle, and astroparticle physics are continuing to advance and are facing unprecedented software challenges due to growing data volumes, complex computing needs, and environmental considerations. As new experiments emerge, software and computing needs must be recognised and integrated early in design phases. This document synthesises insights from ECFA, NuPECC and APPEC, representing particle physics, nuclear physics, and astroparticle physics, and presents collaborative strategies for improving software, computing frameworks, infrastructure, and career development within these fields.

physics.comp-ph↗

arXiv2020

HL-LHC Computing Review: Common Tools and Community Software

Common and community software packages, such as ROOT, Geant4 and event generators have been a key part of the LHC's success so far and continued development and optimisation will be critical in the future. The challenges are driven by an ambitious physics programme, notably the LHC accelerator upgrade to high-luminosity, HL-LHC, and the corresponding detector upgrades of ATLAS and CMS. In this document we address the issues for software that is used in multiple experiments (usually even more widely than ATLAS and CMS) and maintained by teams of developers who are either not linked to a particular experiment or who contribute to common software within the context of their experiment activity. We also give space to general considerations for future software and projects that tackle upcoming challenges, no matter who writes it, which is an area where community convergence on best practice is extremely useful.

physics.comp-ph↗

arXiv2018

A Roadmap for HEP Software and Computing R&D for the 2020s

Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the HL-LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, this white paper describes the R&D activities required to prepare for this software upgrade.

physics.comp-ph↗

arXiv2018

Tunneling spectroscopy of gate-induced superconductivity in MoS$_2$

The ability to gate-induce superconductivity by electrostatic charge accumulation is a recent breakthrough in physics and nano-electronics. With the exception of LaAlO$_3$/SrTiO$_3$ interfaces, experiments on gate-induced superconductors have been largely confined to resistance measurements, which provide very limited information about the superconducting state. Here, we explore gate-induced superconductivity in MoS$_2$ by performing tunneling spectroscopy to determine the energy-dependent density of states (DOS) for different levels of electron density $\textit{n}$. In the superconducting state, the DOS is strongly suppressed at energy smaller than the gap, Δ, which is maximum (Δ~ 2 meV) for $\textit{n}$ of ~ 10$^{14}$ cm$^{-2}$ and decreases monotonously for larger $\textit{n}$. A perpendicular magnetic field $\textit{B}$ generates states at $E<Δ$ that fill the gap, but a 20% DOS suppression of superconducting origin unexpectedly persists much above the transport critical field. Conversely, an in-plane field up to 10 T leaves the DOS entirely unchanged. Our measurements exclude that the superconducting state in MoS$_2$ is fully gapped and reveal the presence of a DOS that vanishes linearly with energy, the explanation of which requires going beyond a conventional, purely phonon-driven Bardeen-Cooper-Schrieffer mechanism.

cond-mat.supr-con↗

arXiv2017

Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength Dependent Mapping

The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys, with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband transitions generate an unbalanced non-equilibrium population of electrons and holes in these valleys, resulting in a finite Hall voltage at zero magnetic field when a current flows through the system. This is the so-called valley Hall effect that has recently been observed experimentally. Here, we show that this effect is mediated by photo-generated neutral excitons and charged trions, and not by inter-band transitions generating independent electrons and holes. We further demonstrate an experimental strategy, based on wavelength dependent spatial mapping of the Hall voltage, which allows the exciton and trion contributions to the valley Hall effect to be discriminated in the measurement. These results represent a significant step forward in our understanding of the microscopic origin of photo-induced valley Hall effect in semiconducting transition metal dichalcogenides, and demonstrate experimentally that composite quasi-particles, such as trions, can also possess a finite Berry curvature.

cond-mat.mes-hall↗

arXiv2015

Gate-induced Superconductivity in atomically thin MoS2 crystals

When thinned down to the atomic scale, many layered van der Waals materials exhibit an interesting evolution of their electronic properties, whose main aspects can be accounted for by changes in the single-particle band structure. Phenomena driven by interactions are also observed, but identifying experimentally systematic trends in their thickness dependence is challenging. Here, we explore the evolution of gate-induced superconductivity in exfoliated MoS2 multilayers ranging from bulk-like to individual monolayers. We observe a clear transition for all the thicknesses down to the ultimate atomic limit, providing the first demonstration of superconductivity in atomically thin exfoliated crystals. Additionally, we characterize the superconducting state by measuring the critical temperature (TC) and magnetic field (BC) in a large number of multilayer devices, upon decreasing their thickness. The superconducting properties change smoothly down to bilayers, and a pronounced reduction in TC and BC is found to occur when going from bilayers to monolayers, for which we discuss possible microscopic mechanisms. Finding that gate-induced superconductivity persists in individual monolayers, which form the basic building blocks of more sophisticated van der Waals heterostructures, opens new possibilities for the engineering of the electronic properties of materials at the atomic scale.

cond-mat.supr-con↗

arXiv2015

Electrostatically Induced Superconductivity at the Surface of WS$_2$

We investigate transport through ionic liquid gated field effect transistors (FETs) based on exfoliated crystals of semiconducting WS$_2$. Upon electron accumulation, at surface densities close to -or just larger than- 10$^{14}$ cm$^{-2}$, transport exhibits metallic behavior, with the surface resistivity decreasing pronouncedly upon cooling. A detailed characterization as a function of temperature and magnetic field clearly shows the occurrence of a gate-induced superconducting transition below a critical temperature $T_c \approx 4$ K, a finding that represents the first demonstration of superconductivity in tungsten-based semiconducting transition metal dichalcogenides. We investigate the nature of superconductivity and find significant inhomogeneity, originating from the local detaching of the frozen ionic liquid from the WS$_2$ surface. Despite the inhomogeneity, we find that in all cases where a fully developed zero resistance state is observed, different properties of the devices exhibit a behavior characteristic of a Berezinskii-Kosterlitz-Thouless transition, as it could be expected in view of the two-dimensional nature of the electrostatically accumulated electron system.

cond-mat.mes-hall↗

arXiv2014

Random strain fluctuations as dominant disorder source for high-quality on-substrate graphene devices

We have performed systematic investigations of transport through graphene on hexagonal boron nitride (hBN) substrates, together with confocal Raman measurements and a targeted theoretical analysis, to identify the dominant source of disorder in this system. Low-temperature transport measurements on many devices reveal a clear correlation between the carrier mobility $μ$ and the width $n^*$ of the resistance peak around charge neutrality, demonstrating that charge scattering and density inhomogeneities originate from the same microscopic mechanism. The study of weak-localization unambiguously shows that this mechanism is associated to a long-ranged disorder potential, and provides clear indications that random pseudo-magnetic fields due to strain are the dominant scattering source. Spatially resolved Raman spectroscopy measurements confirm the role of local strain fluctuations, since the line-width of the Raman 2D-peak --containing information of local strain fluctuations present in graphene-- correlates with the value of maximum observed mobility. The importance of strain is corroborated by a theoretical analysis of the relation between $μ$ and $n^*$ that shows how local strain fluctuations reproduce the experimental data at a quantitative level, with $n^*$ being determined by the scalar deformation potential and $μ$ by the random pseudo-magnetic field (consistently with the conclusion drawn from the analysis of weak-localization). Throughout our study, we compare the behavior of devices on hBN substrates to that of devices on SiO$_2$ and SrTiO$_3$, and find that all conclusions drawn for the case of hBN are compatible with the observations made on these other materials. These observations suggest that random strain fluctuations are the dominant source of disorder for high-quality graphene on many different substrates, and not only on hexagonal boron nitride.

cond-mat.mes-hall↗

arXiv2009

Supersymmetric particle mass measurement with invariant mass correlations

The kinematic end-point technique for measuring the masses of supersymmetric particles in R-Parity conserving models at hadron colliders is re-examined with a focus on exploiting additional constraints arising from correlations in invariant mass observables. The use of such correlations is shown to potentially resolve the ambiguity in the interpretation of quark+lepton end-points and enable discrimination between sequential two-body and three-body lepton-producing decays. The use of these techniques is shown to improve the SUSY particle mass measurement precision for the SPS1a benchmark model by at least 20-30% compared to the conventional end-point technique.

hep-ph↗

arXiv2001

Higgs Physics at the Large Hadron Collider

A major goal of the future Large Hadron Collider will be the Higgs boson search. In this paper the discovery In this paper the discovery potential is described as a function of the Higgs mass showing that a Standard Model Higgs boson can be discovered after less than two years of running of the collider. The MSSM Higgs searches and the precision achievable on the measurement of the Higgs boson parameters are also discussed.

hep-ex↗