Over the past decade or more, there has been a great deal of interest in the mechanical, electronic and optical properties of graphene. The interest in the optical properties of graphene stems largely from two key features of the electronic band structure: it is gapless and the dispersion is linear near the Dirac points where the two bands touch. Both of these features can be uniquely accessed using terahertz radiation, because, under the right conditions, it can strongly drive both interband and intraband transitions. In this talk, I will describe the formalism and computational results of our density-matrix approach to modelling the nonlinear terahertz response of graphene, including various scattering mechanisms. As I will show, in undoped graphene, a very large nonlinearity can arise due to the interplay between the intraband and interband transitions. I will finish by showing how a parallel-plate waveguide configuration containing graphene could be used to generate the third harmonic of a 2 terahertz incident field with a power conversion efficiency of up to 20%. If time allows, I will also discuss our recent results on the effects of impurities and strain on third harmonic generation in graphene.

Come per qualsiasi sistema dinamico, la modellizzazione del clima consiste nella risoluzione delle equazioni differenziali che lo governano, a partire dalle condizioni iniziali e tenendo conto delle condizioni al contorno e del forzante del sistema. Il modello climatico restituisce quindi, istante per istante, lo stato delle variabili climatiche essenziali (ECV) che descrivono la dinamica dell’atmosfera e dell’oceano, tipicamente temperatura, pressione, umidità e velocità del vento. A seconda dell’orizzonte temporale della simulazione, lo stato del sistema è influenzato maggiormente dalle condizioni iniziali (per es. alla scala meteorologica), dalle condizioni al contorno (es. alla scala stagionale) o dal forzante (es. alla scala decennale e multidecennale). In questo seminario saranno presentate le caratteristiche principali del sistema climatico e delle equazioni che lo governano, e come i modelli climatici possano essere utilizzati per produrre l’informazione (ovvero i dati) sullo stato fisico del sistema su diversi orizzonti temporali.

Titolo
Particelle elementari e interazioni fondamentali.

Relatori
E.Budassi, C.Del Pio, A.Gurgone

The 2022 Nobel prize in Physics has acknowledged the fundamental role of Bell’s theorem in physics. It is well understood that the experimental demonstration of the theorem implies the existence of quantum correlations, often known as nonlocal, that cannot be described by classical theories, in which measurement outcomes are predetermined.

In recent years, Bell nonlocal correlations have also acquired the status of information resource, as they are crucial for the construction of quantum information protocols in the device-independent scenario, where no modelling of the devices is assumed in the implementation. Because of this absence of modelling, device-independent protocols offer the strongest form of security attainable in quantum theory.

This seminar provides an introduction to all these concepts, going from quantum foundations to quantum information science and back. The main concepts and tools in the device-independent formalism are explained, together with an overview of the main results and remaining challenges.

The DUNE experiment, currently under construction at Fermilab and at the Sanford Underground Research Facility (SURF), is one of the most ambitious projects ever conceived in neutrino physics. Its physics program ranges from the precision measurement of the neutrino oscillation parameters by means of a broadband beam, to the study of astroparticles through the use of natural sources, to the physics beyond the standard model. Such a wide program is made possible by the large mass of the detector (70 Kt), by its underground location at a depth of 1500 m, by the adoption of the liquid argon TPC technology, by the unprecedented power of the beam and by sophisticated Near Detectors, dedicated to reducing the systematic error. In this seminar we will discuss the performances of DUNE in the determination of neutrino mass ordering and in the study of CP violation in the leptonic sector, in the potential observation of supernova explosions, in proton decay and in the precision studies of atmospheric and solar neutrinos. We will also describe the state of the construction, the results of the prototypes and the future developments of the experiment.

INRIM is the Italian institute devoted to metrology within the International Convention of the Meter. The development and the deployment worldwide of quantum standards is among its core activities, both in fundamental research and services.

The Quantum Metrology Division is deeply committed to new standards, new measurements, and new devices. In particular, in recent years three relevant trends are emerging. First, in the frame of the European Quantum Communication Infrastructure, INRIM is active with the Italian Quantum Backbone research infrastructure and the QKD testing and validation activities; second, the miniaturization trends (also in metrology but not only) led to the new research infrastructure Piquet for quantum, micro and nano devices; third, a growing engagement in the aerospace sector, from Galileo to the new quantum challenges.

The talk will describe INRIM achievements and perspectives on these three
challenges.

The lecture will address applications of nuclear and subnuclear physics technologies to Cultural Heritage and  Environment.

Nuclear techniques for Cultural Heritage are oriented to diagnostics, conservation and restoration of artworks. They also include their non-​destructive compositional analysis which is of great interest both to art historians and restorers. These techniques, and in particular those based on the use of accelerated ion beams to probe the composition of materials, are multi-​elemental, quantitative, very sensitive and fast to perform. They can provide stratigraphic and fine spatially resolved information.

The same techniques are very useful to study the composition of the particulate matter (aerosol) which has natural or anthropic source, thus giving clues on the quality of the air, pollution and possible impacts on climate change.

Examples of specific applications performed at LABEC, the INFN and University of Florence laboratory, will be presented during the seminar.

Titolo
Un nettare per curare l’Alzheimer: la fisica nucleare in soccorso
all’invecchiamento globale.

Relatori
N.Protti, V.Pascali

High-order harmonics are generated from the interaction of intense femtosecond laser pulses with noble gases. Recently, high-order Harmonic Generation (HHG) led to the realization of table-top sources of coherent XUV and Soft-X Ray radiation. With these sources, ultrafast spectroscopy can be performed with extreme temporal resolutions, down to the attosecond regime (1 as = 10^-18 s), and with the site and chemical selectivity. These features grant access to purely electronic dynamics in molecules and solids and fundamental processes of light-matter interaction. Furthermore, HHG has been successfully used as a spectroscopic tool in the gas phase and condensed matter, allowing the study of electron dynamics in a cation following sudden ionization, all-optical band structure reconstruction, and berry phase retrieval. These findings demonstrate the flexibility and potentiality of this technique.

In this colloquium, I will introduce the principle of high-order harmonic generation as a source of XUV radiation and its application for ultrafast XUV spectroscopy and high-order harmonic spectroscopy. I will also report on the most recent developments in ultrafast XUV spectroscopy based on HHG in the Udyni labs [1] at CNR-IFN.

I will describe our recent developments in efficient XUV generation in microfluidic devices fabricated by femtosecond laser irradiation followed by chemical etching [2]. With this approach, we were able to control the harmonic generation process in the gas on the micro-meter scale with high flexibility, enabling a high photon flux and phase matching on broadband harmonics up to 200 eV. This source is part of a new beamline for transient absorption/reflectivity measurements in molecules and solids. I will also describe the beamline developed for HHG spectroscopy in solids available at CNR-IFN and report on preliminary results in dielectrics and semiconductors.

[1] www.udyni.eu

[2] A. G. Ciriolo et al., J. Phys. Photonics 2, 024005 (2020); https://doi.org/10.1088/2515-7647/ab7d81

[3] A. G. Ciriolo et al., APL Photonics 7, 110801 (2022); https://doi.org/10.1063/5.0118199