Category Archives: research

Yambo school 2020: new video lectures and tutorials are online

The “Computational School on Electronic Excitations in Novel Materials Using the Yambo Code” school at the ICTP has just ended. In this school we presented an introduction to many-body theory, a new version of the code that include all the non-linear response part. The new tutorials that are available in the wiki webpage. Moreover all… Read More

Computational School on Electronic Excitations in Novel Materials Using the Yambo Code

The Computational School on Electronic Excitations in Novel Materials Using the Yambo Code, introduces participants to post-DFT simulations, in particular many-body perturbation theory (MBPT) approaches and provide training in the calculation of electronic and optical properties of materials. The program will offer theoretical and technical lectures, as well as dedicated hands-on sessions where the students… Read More

The story of Academic Publishing: from Galileo to Nature

I was invited to give a seminar at the conference of young Italian researchers. At this conference I will present a  talk on the story of academic publishing. I will briflely present the story of academic publising, from the first journals to the modern publication system, passing through open access, impact factor, etc… I show… Read More

Theory of phonon-assisted luminescence

In this presentation I present the theory of phonon-assisted luminescence, in terms of non-equilibrium  Green’s functions and time-dependent perturbation theory. We derived a simple formule for light emission in the limit of low excited carriers including excitonic effects and then included coupling with phonons by time-dependent perturbation theory. This approach is then applied to the… Read More

Luminescence of hexagonal boron nitride explained

Luminescence of hexagonal boron nitride (hBN) has puzzled researchers for long time. In standard solid state physics textbooks direct band gap semiconductors are considered efficient light emitters while indirect ones are regarded as inefficient. Hexagonal boron nitride seems to defy this rule. In fact hBN emits light in the ultraviolet with an efficient comparable to… Read More

Direct and indirect excitons in boron nitride polymorphs: a story of atomic configurations and electronic correlation

In this work we study how different atomic configurations, and electronic correlation modify the exciton dispersion in hexagonal boron nitride. We use two different approaches, ab-initio DFT plus many-body perturbation theory and tight-binding. We found that in the case of AB-stacking electronic correlation inverts the nature of the optical gap, from indirect to direct respect… Read More

OPTEL2D: Opto-electronic properties of 2D Transition Metal Dichalcogenides with DFT and post-DFT simulations

Our Prace research project OPTEL2D “Opto-electronic properties of 2D Transition Metal Dichalcogenides with DFT and post-DFT simulations” has been accepted, and we got 49.5 million core hours on Marconi – KNL.     Here the project description: “Two-dimensional (2D) and layered materials possess novel combinations of electronic and optical properties and thus present a unique… Read More

Two-photon absorption in two-dimensional crystals

In this work we combine tight-binding calculations of the two-photon transition probability with sophisticated ab-initio real-time Bethe-Salpeter simulations of the two-photon resonance third-order susceptibility. This combination is a unique feature of this work: on the one hand the tight-binding calculations allow us to identify the symmetry properties of the excitons, on the other hand the… Read More

Invisible excitons in hexagonal Boron Nitride

New talk for the conference “2D layered materials for opto-electronics: a theoretical/computational perspective” in Rome. In this work we study excitations in hexagonal Boron Nitride that are invisible in linear optical response. We show that these dark states can be measured with other spectroscopic techniques and they play an important roles in the luminescence response… Read More

Exciton interference in hexagonal boron nitride

Our new paper on exciton interference in hexagonal boron nitride is online. In this paper we show  that the excitonic peak  at finite momentum is formed by the superposition of two groups of transitions that we call KM and MK′ from the k-points involved in the transitions. These two groups contribute to the peak intensity… Read More