Author

# Giorgio Pettinari

Other affiliations: Sapienza University of Rome, Radboud University Nijmegen, University of Nottingham

Bio: Giorgio Pettinari is an academic researcher from National Research Council. The author has contributed to research in topics: Band gap & Quantum dot. The author has an hindex of 17, co-authored 89 publications receiving 1040 citations. Previous affiliations of Giorgio Pettinari include Sapienza University of Rome & Radboud University Nijmegen.

Topics: Band gap, Quantum dot, Photoluminescence, Materials science, Hydrogen

##### Papers published on a yearly basis

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23 Jan 2020TL;DR: In this article, the effects of high strain on the optoelectronic properties of 2D crystals were investigated and the possibility to induce a clear-cut crossover from direct to indirect bandgap in strained monolayers was demonstrated.

Abstract: This paper reports the effects of high strains on the optoelectronic properties of 2D crystals. By realizing micro- and nano-domes made of single layer transition-metal dichalcogenides, the authors demonstrate the possibility to induce a clear-cut crossover from direct to indirect bandgap in strained monolayers. The indirect excitons can be harvested and potentially stored for long times, which is relevant for flexible photovoltaics devices and for inducing bosonic condensation.

94 citations

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TL;DR: In this article, the electronic properties of GaAs1−xBix were investigated by photoluminescence at variable temperature (T=10−430K) and high magnetic field (B=0-30T).

Abstract: We investigate the electronic properties of GaAs1−xBix by photoluminescence at variable temperature (T=10–430K) and high magnetic field (B=0–30T). In GaAs0.981Bi0.019, localized state contribution to PL is dominant up to 150K. At T=180K the diamagnetic shift of the free-exciton states reveals a sizable increase in the carrier effective mass with respect to GaAs. Such an increase cannot be accounted for by an enhanced localized character of the valence band states, solely. Instead, it suggests that also the Bloch states of the conduction band are heavily affected by the presence of bismuth atoms.

90 citations

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TL;DR: In this paper, the electron effective mass was determined by magnetophotoluminescence in as-grown and hydrogenated samples for a wide range of nitrogen concentrations (from 0.01% to 1.78%).

Abstract: The electron effective mass, ${m}_{\mathrm{e}}$, has been determined by magnetophotoluminescence in as-grown and hydrogenated $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ samples for a wide range of nitrogen concentrations (from $xl0.01%$ to $x=1.78%$). A modified $\mathbf{k}\mathbf{∙}\mathbf{p}$ model, which takes into account hybridization effects between N cluster states and the conduction band edge, reproduces quantitatively the experimental ${m}_{\mathrm{e}}$ values up to $x\ensuremath{\leqslant}0.6%$. Experimental and theoretical evidence is provided for the N complexes responsible for the nonmonotonic and initially puzzling compositional dependence of the electron mass.

88 citations

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TL;DR: Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor thirty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware.

Abstract: As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds of microseconds, they are currently one of the leading platforms for quantum information processing. However, coherence needs to further improve by orders of magnitude to reduce the prohibitive hardware overhead of current error correction schemes. Reaching this goal hinges on reducing the density of broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source of nonequilibrium quasiparticles. Moreover, ionizing radiation introduces time-correlated quasiparticle bursts in resonators on the same chip, further complicating quantum error correction. Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor fifty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware.

61 citations

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TL;DR: Lithographic techniques provide a means to engineer the formation process so that the domes can be produced with well-ordered positions and sizes tunable from the nanometer to the micrometer scale, with important prospects for so far unattainable applications.

Abstract: At the few-atom-thick limit, transition-metal dichalcogenides (TMDs) exhibit strongly interconnected structural and optoelectronic properties. The possibility to tailor the latter by controlling the former is expected to have a great impact on applied and fundamental research. As shown here, proton irradiation deeply affects the surface morphology of bulk TMD crystals. Protons penetrate the top layer, resulting in the production and progressive accumulation of molecular hydrogen in the first interlayer region. This leads to the blistering of one-monolayer thick domes, which stud the crystal surface and locally turn the dark bulk material into an efficient light emitter. The domes are stable (>2-year lifetime) and robust, and host strong, complex strain fields. Lithographic techniques provide a means to engineer the formation process so that the domes can be produced with well-ordered positions and sizes tunable from the nanometer to the micrometer scale, with important prospects for so far unattainable applications.

60 citations

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TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

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28,685 citations

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TL;DR: In this article, the time dependence of ρ11, ρ22 and ρ12 under steady-state conditions was analyzed under a light field interaction V = -μ12Ee iωt + c.c.

Abstract: (b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

1,872 citations

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TL;DR: In this paper, the bandgap of InN was revised from 1.9 eV to a much narrower value of 0.64 eV, which is the smallest bandgap known to date.

Abstract: Wide-band-gap GaN and Ga-rich InGaN alloys, with energy gaps covering the blue and near-ultraviolet parts of the electromagnetic spectrum, are one group of the dominant materials for solid state lighting and lasing technologies and consequently, have been studied very well. Much less effort has been devoted to InN and In-rich InGaN alloys. A major breakthrough in 2002, stemming from much improved quality of InN films grown using molecular beam epitaxy, resulted in the bandgap of InN being revised from 1.9 eV to a much narrower value of 0.64 eV. This finding triggered a worldwide research thrust into the area of narrow-band-gap group-III nitrides. The low value of the InN bandgap provides a basis for a consistent description of the electronic structure of InGaN and InAlN alloys with all compositions. It extends the fundamental bandgap of the group III-nitride alloy system over a wider spectral region, ranging from the near infrared at ∼1.9 μm (0.64 eV for InN) to the ultraviolet at ∼0.36 μm (3.4 eV for GaN...

871 citations