- My major research interest is the application of Many-Body techniques to Condensed matter physics and nanoscience. In particular the description and prediction of the ground-state, electronic and spectroscopic properties of solids and nanomaterials. I am especially interested in studying the fundamentals of many body perturbation theory and static as well as time-dependent Density Functional Theory (DFT and TDDFT).
- My current research topics are non-linear and ultra-fast electronic processes: second-harmonic generation, optical gain, optical switches and real-time femtosecond dynamics.
- I have been member of the Condensed Matter Theory Group of the Physics Department of the University of Rome Tor Vergata, and of the European Theoretical Spectroscopy Facility.
- Exciton collapse by Pauli blocking in hexagonal BN
A. Marini, work in progress
What happens when an ultra-strong laser pulse shine a material with an energy resonant with the excitonic energy? It happens that the excitons collapses as a consequence of the reduction of the phase-space associated to the excitonic state.
- Phonon-induced dephasing in electronic systems excited out-of-the-equilibrium by means of intense laser pulses
A. Marini, work in progress
Ultra-fast optical spectroscopy is a powerful tool for the observation of dynamical processes in several kind of materials. The basic time-resolved optical experiment is the so-called “pump-probe”: a first light pulse, the “pump”, resonantly triggers a photo-induced process. The probe pulse photon energy, spectral width and peak intensity creates a certain density of electron-hole pairs in a more or less localized region of space. The subsequent system evolution can be monitored, for example, by the time-dependent transmission changes of a delayed “probe” pulse. After the creation of the initial carrier density the time evolution of the single-particle and many-particle excitations is now governed by a non-trivial interplay between phase coherence and energy relaxation. Indeed, scattering processes tend to destroy the coherence, leading to a de-phasing of the excitations. The role of the electronic correlations at this stage is to stabilize the ensemble by creating quasi-particles and multi-particle states De-phasing will be driven by different phenomena. One of the most important is the energy transfer to the atomic motion in form of phonon excitations. In this research project I am studying a novel approach based on the merging of Non-Equilibrium Green’s function theory and Density Functional Theory to treat the phonon-mediated relaxation following the pump excitation. I am analyzing theoretical and methodological aspects of the basic tools, the Kadanoff-Baym equations (KBE), and doing simulations of the pumped electrons dynamics in paradigmatic materials.
- Real-time approach to the optical properties of solids and nanostructures: Time-dependent Bethe-Salpeter equation
C. Attaccalite, M. Gruning, and A. Marini, Phys. Rev. B 84, 245110 (2011).
Many-body effects are known to play a crucial role in the electronic and optical properties of solids and nano-structures. Nevertheless the majority of theoretical and numerical approaches able to capture the influence of Coulomb correlations are restricted to the linear response regime. In this work we introduce a novel approach based on a real-time solution of the electronic dynamics. The proposed approach reduces to the well-known Bethe-Salpeter equation in the linear limit regime and it makes possible, at the same time, to investigate correlation effects in nonlinear phenomena. We show the flexibility and numerical stability of the proposed approach by calculating the dielectric constants and the effect of a strong pulse excitation in bulk h-BN.