Nuova ricerca

MATTEO ZANFROGNINI

Home | Curriculum(pdf) |


Pubblicazioni

2023 - Effect of uniaxial strain on the excitonic properties of monolayer C3N: A symmetry-based analysis [Articolo su rivista]
Zanfrognini, M; Spallanzani, N; Bonacci, M; Molinari, E; Ruini, A; Caldas, Mj; Ferretti, A; Varsano, D
abstract

In recent years, the application of mechanical stress has become a widespread experimental method to tune the electronic and optical properties of two-dimensional (2D) materials. In this work, we investigate the impact of uniaxial tensile strain along zigzag and armchair directions on the excitonic properties of graphene-like C3N, a single-layer indirect-gap material with relevant mechanical and optical properties. To do that, we develop a tight -binding Bethe-Salpeter equation framework based on a Wannier-function description of the frontier bands of the system, and use it to compute both dark and bright excitons of C3N for different applied strain configurations. Then, we use this model approach to classify excitons of pristine and strained C3N according to the crystal symmetry and to explain the appearance of bright excitons with intense optical anisotropy in strained C3N, even at small strains. Finally, the effect of strain on the exciton dispersion at small center-of-mass momenta is discussed, with special focus on the implications for 2D linear-nonanalytic dispersions.

2022 - Excitonic effects in graphene-like C3N [Articolo su rivista]
Bonacci, Miki; Zanfrognini, Matteo; Molinari, Elisa; Ruini, Alice; Caldas, Marilia J.; Ferretti, Andrea; Varsano, Daniele
abstract

2020 - Combination of Electron Energy-loss Spectroscopy and Orbital Angular Momentum Spectroscopy. Applications to Electron Magnetic Chiral Dichroism, Plasmon-loss, and Core-loss [Articolo su rivista]
Bertoni, G.; Rotunno, E.; Tavabi, A.; Zanfrognini, M.; Rosi, P.; Frabboni, S.; Karimi, E.; Dunin-Borkowski, R.; Grillo, V.
abstract

2020 - Dynamical diffraction effects in STEM orbital angular momentum resolved electron energy-loss magnetic chiral dichroism [Articolo su rivista]
Zanfrognini, M.; Rotunno, E.; Rusz, J.; Dunin Borkowski, R. E.; Karimi, E.; Frabboni, S.; Grillo, V.
abstract

In this paper, we explore the properties of dynamical diffraction coefficients in orbital angular momentum resolved electron energy-loss magnetic chiral dichroism spectra, in a scanning transmission electron microscopy setup. We demonstrate that for basic zone axis geometries with fourfold or threefold symmetry the coefficients are constrained to have simplified forms. By exploiting these properties, we show how a dichroism spectrum accessible using this technique is only weakly dependent on sample thickness and, more generally, on dynamical diffraction effects. Our results indicate that in such cases it is possible to determine the orbital and spin components of atomic magnetic moments approximately from experimental spectra without the need for additional dynamical diffraction calculations.

2019 - Orbital Angular Momentum and Energy Loss Characterization of Plasmonic Excitations in Metallic Nanostructures in TEM [Articolo su rivista]
Zanfrognini, Matteo; Rotunno, Enzo; Frabboni, Stefano; Sit, Alicia; Karimi, Ebrahim; Hohenester, Ulrich; Grillo, Vincenzo
abstract

Recently, a new device to measure the orbital angular momentum (OAM) electronic spectrum after elastic/inelastic scattering in a transmission electron microscope has been introduced. We modified the theoretical framework needed to describe conventional low-loss electron energy loss spectroscopy (EELS) experiments in transmission electron microscopes (TEM) to study surface plasmons in metallic nanostructures, to allow for an OAM post selection and devise new experiments for the analysis of these excitations in nanostructures. We found that unprecedented information on the symmetries and on the chirality of the plasmonic modes can be retrieved even with limited OAM and energy resolutions.

2019 - Orbital angular momentum resolved electron magnetic chiral dichroism [Articolo su rivista]
Rotunno, E.; Zanfrognini, M.; Frabboni, S.; Rusz, J.; Dunin Borkowski, R. E.; Karimi, E.; Grillo, V.
abstract

We propose to use the recently introduced orbital angular momentum spectrometer in a transmission electron microscope to perform electron magnetic chiral dichroism experiments, dispersing the inelastically scattered electrons from a magnetic material in both energy and angular momentum. The technique offers several advantages over previous formulations of electron magnetic chiral dichroism as it requires much simpler experimental conditions in terms of specimen orientation and thickness. A simulation algorithm, based on the multislice description of the beam propagation, is used to anticipate the advantages of the approach over current electron magnetic chiral dichroism implementations. Numerical calculations confirm an increased magnetic signal to noise ratio with in plane atomic resolution.