Federico Mazzola's area of research focuses on the electronic structure and properties of quantum materials ranging from semiconductors, semimetals, topological insulators to superconductors, with particular interest in the many-body interactions that underpin their physical properties and how these can be tuned using quantum confinement and modifying their crystalline symmetry. His work is motivated by the synthesis and study of novel systems, which could provide a suitable platform for integration with existing semiconductor-based technology.
2016 - Ph.D. in Physics at the Norwegian University of Science and technology (NTNU), Norway
2012 - Master's Degree in Physics at the Sapienza University of Rome, Italy
2010 - Bachelor Degree in Physics at the Sapienza University of Rome, Italy
Probing the energy and spin electron properties of materials by means of photoemission spectroscopy gives insights into the low-energy phenomena of matter driven by spin orbit coupling or exchange interaction. The information that can be derived from complete photoelectron spectroscopy experiments, beyond E(k), is contained in the photoemission transition matrix elements that determine peak intensities. We present here a complete photoemission study of the spin-polarized bands of 2H−NbSe2, a material that presents a surface spin-texture. Circular dichroism in angular-resolved photoemission spectroscopy (CD-ARPES) data are compared with spin-polarized angular-resolved spectra (SARPES) as measured with linearly polarized radiation in a well-characterized experimental chirality, at selected photon energy values. CD-ARPES is due to a matrix element effect that depends strongly on photon energy and experimental geometry: we show that it cannot be used to infer intrinsic spin properties in 2H−NbSe2. On the other hand, SARPES data provide reliable direct information on the spin properties of the electron states. The results on 2H−NbSe2 are discussed, and general methodological conclusions are drawn on the best experimental approach to the determination of the spin texture of quantum materials.
We investigate the temperature-dependent electronic structure of the van der Waals ferromagnet, CrGeTe3. Using angle-resolved photoemission spectroscopy, we identify atomic- and orbital-specific band shifts upon cooling through TC. From these, together with x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we identify the states created by a covalent bond between the Te 5p and the Cr eg orbitals as the primary driver of the ferromagnetic ordering in this system, while it is the Cr t2g states that carry the majority of the spin moment. The t2g states furthermore exhibit a marked bandwidth increase and a remarkable lifetime enhancement upon entering the ordered phase, pointing to a delicate interplay between localized and itinerant states in this family of layered ferromagnets.
Among transition-metal dichalcogenides, mono and few-layers thick VSe2 has gained much recent attention following claims of intrinsic room-temperature ferromagnetism in this system, which have nonetheless proved controversial. Here, we address the magnetic and chemical properties of Fe/VSe2 heterostructure by combining element sensitive x-ray absorption spectroscopy and photoemission spectroscopy. Our x-ray magnetic circular dichroism results confirm recent findings that both native mono/few-layer and bulk VSe2 do not show intrinsic ferromagnetic ordering. Nonetheless, we find that ferromagnetism can be induced, even at room temperature, after coupling with a Fe thin film layer, with antiparallel alignment of the moment on the V with respect to Fe. We further consider the chemical reactivity at the Fe/VSe2 interface and its relation with interfacial magnetic coupling.