Workshop on Spectroscopy and Dynamics of Photoinduced Electronic Excitations

From the 8th to the 12th May, over 100 scientists from over 30 countries have gathered at the Abdus Salam ICTP in Trieste, Italy, to attend the Workshop on Spectroscopy and Dynamics of Photoinduced Electronic Excitations. This workshop had the goal to put together experts in investigation of photoinduced electronic excitations in real materials. This field has experienced tremendous progress recently, mainly thanks to developments in experimental techniques, like ultrafast spectroscopy, and in theoretical methods, like many-body perturbation theory and time-dependent density functional theory. Processes of interest include photoabsorption, exciton dynamics, and charge transfer. These issues are of interest for fundamental research, but are also relevant for applications in photovoltaics, optoelectronics, and photocatalysis. The workshop consisted of lectures from leading experts in both theoretical and experimental research, and seminars on career development.

Scientific program

The workshop has covered recent developments which make it now possible to study excited state dynamics at very short time scales, clarifying processes taking place in materials ranging from inorganic semiconductors to systems of biological interest.

In the opening session, Matthew C. Beard (National Renewable Energy Laboratory) and David Cahen (Weizmann Institute of Science) presented progress in the investigation optical and optoelectronic properties of quantum dots, perovksites and proteins. This was a fitting way to start, as it presented all relevant classes of materials for the workshop (inorganic, biological, and hybrid organic-inorganic materials), and the processes of interest, including photoabsorption, multi-exciton generation, and charge dynamics. The day was completed with a deeper view at ultrafast spectroscopy with talks by Giulio Cerullo (Politecnico di Milano), Ralph Ernstorfer (Fritz Haber Institute), and Elisabetta Collini (University of Padova), who spoke also about quantum-coherent dynamics in biological photosystems.

The second day was galvanized by theoretical talks by E.K.U. Gross (MPI for Microstructure Physics) on laser-induced spin dynamics, Oleg Prezhdo (University of Southern California) on time-domain investigations on charge transfer in nanostructures, and Claudia Draxl (Humboldt University) on core-level excitations. An experimental view on processes in organic photovoltaics was given by Niyazi Serdar Sariciftci (Johannes Kepler University Linz) and Vladimir Dyakonov (University of Würzburg). The alternation of talks by theoreticians and experimentalists was key to a better exchange of ideas. The day was closed by the session “Career perspectives for young scientists”, where Claudia Draxl (Humboldt University) and Elisabetta Collini (University of Padova) gave their perspective on career strategies, mentoring, women in science, career-life balance, and discrimination on the workplace.

On the third day, Kevin Sivula (EPFL) gave an illuminating talk over charge dynamics in oxides and chalcogenides in the context of photoelectrochemical applications, while Daniele Fausti (University of Trieste, and Elettra Synchrotron) spoke about optical control of quasiparticle population in strongly correlated electron systems. Michael Strano (MIT) gave an inspiring overview over his research at the boundary of physics, chemistry and engineering. Developments in the understanding of exciton dynamics, dissociation and charge transport were discussed by Elisa Molinari (University of Modena), Jochen Blumberger (University College London), and Letizia Chiodo (UCBM University Campus Bio-Medico of Rome). Finally, progress in the simulations of high-harmonic generation in solids was presented by Nicolas Tancogne-Dejean (MPI for the Structure and Dynamics of Matter).

On Thursday, Steven Louie (UC Berkeley) and Lucia Reining (Ecole Polytechnique) talked about many-body perturbation theory, while Angel Rubio (MPI for the Structure and Dynamics of Matter, and UPV/EHU) presented new developments aiming at building bridges between quantum optics and time-dependent density functional theory. Stefano Baroni (SISSA) talked about the prediction of materials colours through simulations, while Irene Burghardt (Goethe University Frankfurt) presented advanced methods to describe the quantum dynamics of electronic excitations in polymers. Mikaël Kepenekian (CNRS Institut des Sciences Chimiques de Rennes) closed the session with a seminar on excitons in hybrid perovskites.

Artem Bakulin (Imperial College London) opened the last day with a talk on vibronic phenomena in organic materials, followed by Reinhard Scholz (TU Dresden). Feliciano Giustino (University of Oxford) turned the topic back to oxides, and the transition from polarons to Fermi liquid behaviour in titanium dioxide. Leeor Kronik (Weizmann Institute of Science) presented new proposals for optimal hybrid functionals for a proper description of band gaps in semiconductors, and Johannes Lischner (Imperial College) closed the workshop discussing band alignment at solid-liquid interfaces.

Conclusion

Throughout the workshop, ample time was given to foster scientific discussion, during sessions, coffee breaks, lunch breaks and poster sessions, and participants made good use of this time leading to a very creative and fruitful atmosphere. As a final note, this workshop brought together leading figures in the development of theoretical and experimental methods, as well as in applications, and it has given a good contribution in providing the participants with an overview over different approaches to and issues in materials research, stimulating them to think beyond their specialized field and simulations methods. We are confident that this will generate new collaborations and change many participants’ approach to materials research in the next future.

Event website

Event website, with program and list of participants: http://indico.ictp.it/event/7961/

Full program, with abstracts and presentations: http://indico.ictp.it/event/7961/other-view?view=ictptimetable

Full list of participants: http://indico.ictp.it/event/7961/material/6/

Talks presented (abstracts and slides can be found on the school website):

Matthew C. Beard (National Renewable Energy Laboratory)
High efficiency approaches to solar energy conversion using quantum dots and perovskites

David Cahen (Weizmann Institute of Science)
Proteins as optoelectronic materials?

Giulio Cerullo (Politecnico di Milano)
Snapshots of primary photoinduced events in biomolecules by tunable few-optical-cycle pulses

Elisabetta Collini (University of Padova)
Role of scaffold flexibility and disorder in the coherent dynamics of bio-mimetic systems

Ralph Ernstorfer (Fritz Haber Institute)
Momentum-resolved view on electrons, phonons and their coupling in WSe2 through ultrafast techniques

E.K.U. Gross (MPI for Microstructure Physics)
Laser-induced spin dynamics at the femto-second time scale: Understanding switching mechanisms with real-time TDDFT

Oleg Prezhdo (University of Southern California)
Time-domain ab initio studies of excited state dynamics in nanoscale materials for photovoltaic applications

Claudia Draxl (Humboldt University)
Many-body approach to core-level excitations

Niyazi Serdar Sariciftci (Johannes Kepler University Linz)
Hydrogen bonded bio-organic semiconductors

Vladimir Dyakonov (University of Würzburg)
On the role of spin states in charge transfer reactions in organic photovoltaics and electroluminescence

Claudia Draxl (Humboldt University)
Can we plan a scientific career? And how would we do it?

Elisabetta Collini (University of Padova)
God bless the Australian algae

Kevin Sivula (EPFL)
Charge transport, transfer and recombination in solution-processed oxide and chalcogenide semiconductors for photoelectrochemical application

Daniele Fausti (University of Trieste, and Elettra Synchrotron)
Optical control and quasiparticle witnessing in strongly correlated electron systems

Michael Strano (MIT)
Understanding and engineering the nanoparticle corona and its effect on biological interfaces

Jochen Blumberger (University College London)
Charge transport in organic molecular materials from fragment orbital-based non-adiabatic molecular dynamics simulation

Letizia Chiodo (UCBM University Campus Bio-Medico of Rome)
Anomalous excitons in titanium doxide

Nicolas Tancogne-Dejean (MPI for the Structure and Dynamics of Matter)
High-harmonic generation in solids

Steven Louie (UC Berkeley)
Ab initio studies of excited-state phenomena: GW, GW-BSE, and beyond

Lucia Reining (Ecole Polytechnique)
Dynamical effects in electron spectroscopies

Angel Rubio (MPI for the Structure and Dynamics of Matter, and UPV/EHU)
Ab-initio spin and time-resolved ARPES in real materials with QED-TDDFT: driving WSe2 out of equilibrium

Stefano Baroni (SISSA)
A multiscale approach to the simulation of the optical properties of complex molecules in solution

Irene Burghardt (Goethe University Frankfurt)
High-dimensional quantum dynamics of functional organic polymer materials: coherence, localization, and (dis)order

Mikaël Kepenekian (CNRS Institut des Sciences Chimiques de Rennes)
An approach to excitons in layered hybrid perovskites

Artem Bakulin (Imperial College London)
Vibronic phenomena for charge and energy transfer in organic optoelectronic materials

Feliciano Giustino (University of Oxford)
Crossover from polarons to Fermi liquids in transition metal oxides

Reinhard Scholz (TU Dresden)
Intermolecular and intramolecular charge transfer states in organic electronics

Leeor Kronik (Weizmann Institute of Science)
Optimally-tuned screened range-separated hybrid functionals: theory and applications to solids and interfaces

Johannes Lischner (Imperial College)
Band alignment at solid-liquid interfaces and nanoplasmonic photocatalysis

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