In the image on the right transient reflectivity signal of bulk silicon, computed at the Bethe-Salpeter, level due to the non-equilibrium carriers distribution at 200 fs from the maximum of the laser pulse. Image from Phys. Rev. B 93, 195205 (2016). The results of the simulations are directly compared with the signal collected by the experimental measurements performed by S. Dal Conte (Politecnico di Milano, Italy).

Davide Sangalli moved at the ISM in Montelibretti within the FIRB projec FLASH-IT, whose aim is the first principles description of out-of-equilibrium dynamics of electrons in the ultra-short (atto/femto-second) time domain. The work was done in close collaboration with the experimental group of the Politecnico di Milano.

Here a representation of the electrons and holes occupations on the band structure of bulk silicon at different time snapshots after the action of an ultra-short laser pulse. Image from EPL 110, 47004 (2015). 

Time-resolved sImulations of ultrafast phenoMena in quantum matErialS (TIMES) is an MSCA - DN founded byt the Marie Curie program. 11 PhD positions, with a very competitive salary, have been funded across 10 different institutions. The PhD student working under my supervision will focus on modelling couple exciton-ion dynamics via Ehrenfest combined with time-dependent hartree+sex (E-TD-HSEX) as implemented in the real time module of the yambo code. A close collaboration with E. Perfetto (Rome) and A. Molina-Sanchez (Valencia) and their PhD students is foreseen.

Please apply through the form in the TIMES website

 MAterials design at the eXascale (MAX) is a European Centre of Excellence which enables materials modelling, simulations, discovery and design at the frontiers of the current and future High Performance Computing (HPC), High Throughput Computing (HTC) and data analytics technologies.

A post-doc position is open to work on the yambo code in collaboration with F. Paleari, D. Varsano and A. Ferretti in Modena. The position is foreseen to focus on different aspects: (i) technical details of the implementations and porting of the code on GPUs, (ii) finalizing the implementation of exciton-phonon coupling with applications on 2D materials, and (iii) working on real time exciton-ion coupling in close collaboration with the PhD candidate of the TIMES Network. Depending on the attitude and background of the candidate the focus can be shifted among these three topics.

Interest candidates can contact me at my email address.

Exploring extreme ultraviolet excitons with attosecond time resolution (EXATTO).

Excitons in the extreme-ultraviolet window (or XUV-excitons) offer an ideal playground to explore exciton physics, which is important both at the fundamental level and for many technological applications. Indeed, very recent experimental works started to explore the non-equilibrium dynamics of XUV-excitons by means of pump and probe experiments [1-6]. So far, these experimental results have been interpreted in terms of simple and ad-hoc models. Adequate theoretical methods able to describe non-equilibrium dynamics of XUV-excitons in complex materials are still missing.

In the EXATTO project, we develop first principles methods for material science applications, able to model XUV-excitons both at equilibrium and out of equilibrium. The approach is based on Many Body Perturbation Theory (MBPT), the state-of-the-art computational scheme to model excitons in complex materials, via the solution of the ab initio Bethe-Salpeter Equation (ai-BSE), at equilibrium, and via the real-time propagation of the nonequilibrium Green functions (NEFG) equations, able to model exciton generation and detection. Both BSE and NEGF are implemented in the Yambo code and, their extension and application to model XUV-excitons, will constitute the main goal of the present proposal.

Eigenvalue problems lie at the core of many physical applications and beyond. While often hermitian matrices (HMs) appear, more in general, broader classes of matrices need to be studied. The IsolvBSE project addresses the class of structured pseudo-hermitian matrices (SPHMs). SPHMs emerge, for example, when studying interacting particle-hole hamiltonians, whose eigenvalues and eigenvectors need to be computed to determine the optical properties of materials.

Nowadays, when SPHMs need to be solved, algorithms for non-hermitian matrices (NHMs) are frequently used. Indeed, specific algorithms for SPHMs have been developed only for full diagonalization. For the case of particle-hole hamiltonians, a specific iterative algorithm for SPHMs has also been developed. However, while the algorithm has been very successful, it does not give access to eigenvalues and eigenvectors of the matrices, which are often also needed.

IsolvBSE will develop a novel algorithm able to provide, via an iterative approach, a subset of the eigenvalues and eigenvectors, specific for SPHMs.  This novel algorithm for SPHMs will be directly coded inside the SLEPc library, thus ensuring that it will be made publicly available to the community and distributed. Moreover we will call it via a simple subroutine, which will be embedded in the yambo code. The latter is already interfaced with the SLEPc library, and this structure will ensure a smooth transition towards realistic applications in the future.