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Davide Sangalli

External links:

CNR (Iris)

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Web Of Science

ORCID

arXiv

Scopus

Contacts:

email: davide.sangalli at ism.cnr.it

Since 2016 Davide Sangalli is researcher of the Istituto di Struttura della materia (ISM -CNR), in Piazza Leonardo da Vinci 32, 20133, Milano. He has an active collaboration with the Physics department of Milano Politecnico and the Istituto per la Fotonica e le Nanostrutture (IFN - CNr). He is also a guest researcher at the Milan Lab for Materials simulations in the Physics department of the Università degli Studi di Milano.

 Research activity

Many-Body physics from first principles: correlation effects in semiconductors and nanostructures. Nonequilibrum physics and ultrafast phenomena: carrier dynamics, exciton dynamics, coherent dynamics, quantum kinetics, magnetization dynamics, transient spectroscopy. Emergent physics in condensed matter. Berry-Phase, Kerr effect and Anomalous Hall effects in 3D materials; Kerr effect and valley physics in 2D materials; Gauge invariance out of equilibrium, Aharonov Bohm effect and excitonic insulator phase in 1D carbon nanotubes. Development and exploitation of advanced first-principles computational methods beyond density functional theory, mostly many-body perturbation theory, to study electronic and optical spectroscopies. Scientific software development and high-performance computing.

Nonequilibrium Excitons:

generation and detection

Exciton are bound states of electrons and holes. At equilibrium excitons can be detected in absorption experiments, while angle resolver photo-emission (ARPES) is dominated by quasi-particles peaks. Out of equilibrium instead, excitons can be probed in time-resolved (TR)-ARPES excitons. A laser pulse with energy resonant with the excitonic peak generates a coherent state which can be interpreted as a Bose-Einstein condensate (BEC) of excitons which leaves a clear fingerprint in TR-ARPES.

The activity is done in collaboration with E. Perfetto and G. Stefanuccci (Università di Roma Tor Vergata, Italy), C. Attaccalite  (CINaM - CNRS, Marseille, France), and M. D'Alessandro (ISM - CNR, Roma, Italy)

The image on the left shows the computed exciton TR-ARPES bulk lithium fluoride after the action of a pump laser pulse. In the simulation the pump laser pulse is resonant with the energy of the 1s exciton. The exciton photo-emission signal (upper panel) is a replica of the valence band signal (lower panel) weighted by the excitonic wave–function. The distance from the conduction band minima corresponds to the binding energy of the exciton. Image from Phys. Rev. Mat. 3, 124601 (2020)

Related publications:

  • Phys. Rev. Mat. 5, 083803 (2021)

  • Phys. Rev. Mat. 3, 124601 (2020)

  • Eur. Phys. J. B 91, 171 (2018)

Exciton-phonon coupling

Correctly modelling the coupling of excitons with phonons is a very active research area within the community of material science. There are ongoing developments both on the theoretical site and on the more technical implementation aspects. I'm co-author of a series of publications where the exciton-phonon is studied with different approaches, both in the non-coherent and in the coherent regime. The activity is done in collaboration with C. Attaccalite (CINaM - CNRS, Marseille, France), F. Paleari (NANO - CNR, Modena, Italy), M. Bernardi (Caltech university, USA) and A. Molina-Sanchez (University of Valencia, Spain).

For more info see related publications:

  • Phys. Rev. Mat. 7, 024006 (2023) (arXiv 2212.10407)

  • Phys. Rev. Res. 4, 043203 (2022) (arXiv 2210.05964)

The ongoing implementation is realesed in a fork of the yambo code developed in collaboration with, C. Attaccalite and F. Paleari

https://github.com/sangallidavide/yambo/tree/phys-exc-ph 

You can also check this tutorial:

https://www.yambo-code.eu/wiki/index.php/Exciton-phonon_coupling_and_luminescence 

Finally exciton-phonon is explored in collaboration with experimental groups doing pump and probe measurements. S. Dalcone (Politecnico of Milano), and S. Pagliara (Università Cattolica di Brescia).

Time resolved absorption

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).

Ultra-fast carriers dynamics

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). 

Magneto-optics and dichroism

Work in progress

Optical properties and Excitons

in advanced materials

Work in progress

Magnons

Work in progress

Funded projects and positions

TIMES (2024 - 2029)

[1 PhD position (closed)] 

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

MaX (2023 - 2028)

[1 Post-doc position (closed)]

 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.

EXATTO (2025 - 2027)

[1 Post-doc position]

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.

Isolv-BSE (2024)

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.

TUMIEE cost action (2018 - 2023)

[funding for travelling]

The TUMIEE cost action

PRIN BIOX (2019 - 2023) 

[1 Post-doc position (closed)]

The target of the project is the investigation, with extreme temporal resolution, of the molecular processes initiated by the interaction of ionizing radiation with biologically relevant molecules. The main objective is to identify and control at molecular level the early steps of light-driven processes of primary importance in photochemistry and photobiology, which typically evolve on timescales ranging from theattosecond domain of purely electron dynamics, to the hundreds of femtosecond domain of nuclear dynamics. The experimental strategy is based on the combination of advanced time-resolved techniques, characterized by extreme temporal resolution (from a few femtoseconds to a few hundreds of attoseconds), with synchrotron-based spectroscopic techniques to unravel the molecular mechanisms leading to photo-protection or damage of bio-relevant molecules. Advanced numerical modelling, based on a novel and unique theoretical approach which takes into account the atomistic details of the molecular structure, the action of the extreme-ultraviolet and ultrashort excitation, electron correlation effects and the coupling between electronic and nuclear degrees of freedom, will support and guide the experimental activity.

An ad-hoc version of the yambo code was developed for dealing with isolated systems. If you are interested please download the phys-cichroism branch of my personal for of the yambo code: https://github.com/sangallidavide/yambo/tree/phys-dichroism .

External links:

  • https://www.ism.cnr.it/en/research/projects/item/156-predicting-and-controlling-the-fate-of-bio-molecules-driven-by-extreme-ultraviolet-radiation.html

The Yambo project

Davide Sangalli is one of the main developers of the yambo code also taking care of the administration of the yambo github repository.

Workshop, schools, meetings & more

Workshop: Frontiers in many-body excited-state dynamics from first principles, Lausanne, 15-17 July 2024 [invited]

Workshop: 27th ETSF Workshop on Electronic Excitations, Marseille, 25-29 May 2024 [contributed]

Hackathon: MaX Hackathon: Mini-Apps and CI/CD, April, 15-19 April 2024

Project meetings: TIMES and IsolvBSE kick-off meetings, February, 25-27 February 2024

Workshop: Magnons and magnetismo in 2D materials, Valencia, 18-19 Ottobre 2023 [organizer]

Workshop: Atto2Nano: modeling ultrafast dynamics across time-scales in condensed matter, Lausanne, 26-29 September 2023 [organizer]

MiniColloquium: Exciton Dynamics and transport in quantum materials, Milano, Fismat, 4-8 September 2023 [organizer]

International School: Ab initio many-body perturbation theory: from equilibrium to time-resolved spectroscopies and nonlinear optics, Roma, 22-26 May 2023 [organizer]

Publications

V. Gosetti, J. Cervantes-Villanueva, S. Mor, D. Sangalli, A. García-Cristóbal, A. Molina-Sánchez, V. F. Agekyan, M. Tuniz, D. Puntel, W. Bronsch, F. Cilento, S. Pagliara, Unveiling exciton formation: exploring the early stages in time, energy and momentum domain

submitted (2025) (arXiv 2412.02507)

R. Reho, A. Botello-Méndez, DS, M. Verstraete, Z. Zanolli, Excitonic response in transition metal dichalcogenide heterostructures from first principles: Impact of stacking, twisting, and interlayer distance

Phys. Rev. B 110, 035118 (2024),  [Editor's suggestion]  (arXiv 2404.17182)

V. Gosetti, J. Cervantes-Villanueva, DS, A Molina-Sánchez , V. Agekyan, C. Giannetti, L. Sangaletti, S. Mor, S. Pagliara, Detection of a Coherent Excitonic State in the Layered Semiconductor BiI3

ACS Photonics 11, 2513 (2024)  (arXiv 2311.11964)

J. Cervantes-Villanueva, F. Paleari, A. García-Cristóbal, DS, A. Molina-Sánchez, Excitons in layered : Effects of dimensionality and crystal anisotropy

Phys. Rev. B 109 , 155133 (2024)  (arXiv 2310.16024)

DS, M. D'Alessandro, C. Attaccalite, Exciton-exciton transitions involving strongly bound excitons: An ab initio approach

Phys. Rev. B 107, 205203 (2023)  (arXiv 2211.12241)

S. Di Sabatino, A. Molina-Sánchez, P. Romaniello, DS, Assignment of excitonic insulators in ab initio theories: The case of NiBr2

Physical Review B 107, 115121 (2023) [Editor's suggestion] (arXiv 2212.11500)

P. Lechifflart, F. Paleari, DS, C. Attaccalite, First-principles study of luminescence in hexagonal boron nitride single layer: Exciton-phonon coupling and the role of substrate", Phys. Rev. Mat. 7, 024006 (2023) (arXiv 2212.10407)

C. J. Sayers, A. Genco, C. Trovatello, S. Dal Conte, V. Khaustov, J. Cervantes-Villanueva, DS, A. Molina-Sanchez, C. Coletti, C. Gadermaier, G. Cerullo , Strong Coupling of Coherent Phonons to Excitons in Semiconducting Monolayer MoTe2,

Nano Lett. 23, 9235 (2023) (arXiv 2302.07561)

H.-Y. Chen, DS, M. Bernardi, First-principles ultrafast exciton dynamics and time-domain spectroscopies: Dark-exciton mediated valley depolarization in monolayer

Phys. Rev. Res. 4, 043203 (2022) (arXiv 2210.05964)

E. Molteni, G. Cappellini, DS, Ab initio circular dichroism with the Yambo code: applications to dipeptides,

IOP Conference Series: Materials Science and Engineering 1265, 012005 (2022) (arXiv 2202.02079 )

M. D'Alessandro, DS, Real-time ab initio description of the photon-echo mechanisms in extended systems: the case study of bulk GaAs,

SciPost Physics 12, 193 (2022), (arXiv 2112.13673)


E. Molteni, G. Mattioli, DS, Ab initio Circular Dichroism with the Yambo code: beyond the Independent Particle approximation,

Il Nuovo Cimento C, 175 (2022) (arXiv 2202.12702)


I. M. Alliati, DS, M. Grüning, Double k-Grid Method for Solving the Bethe-Salpeter Equation via Lanczos Approaches,

Frontiers in Chemistry 9, 763946 (2022) (arXiv 2108.11174)


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