Control of Ultrafast (Attosecond and Strong Field) Processes Using Structured Light

Workshop Report

Control of Ultrafast Attosecond and Strong Field Processes using Structured Light

International Seminar and Focus Workshop
Scientific coordinators: Misha Ivanov, Carlos Hernandez-Garcia, and Anthony F Starace†

Attosecond and strong field physics are evolving in several new directions, unified by the goal
of sub-femtosecond control of the electronic response of matter, from atoms to chiral molecules
to quantum solid-state materials, using laser light structured in time and space to induce desired
dynamics. The meeting aimed at bringing together three communities, those of structured light,
attosecond and strong-field physics, and quantum solids, to foster interactions between them.

Attosecond and strong field physics are evolving rapidly in several new directions, unified by the concept of lightwave
electronics: the sub-femtosecond imaging and control of the electronic response of matter, from atoms to chiral
molecules to quantum solids, using laser light structured in time and space to induce and resolve the desired dynamics.
In paralell, new theoretical models and approximations are required to tackle these exciting as well as complex ultrafast
Therefore, the aim of the meeting was to bring together scientists from these three different and rarely interacting
• structured light,
• attosecond and strong-field physics, and
• quantum solid state materials,
providing enough time for fostering their interaction and laying the foundation for developing collaborations between

With this goal in mind, the meeting included a 3-week long symposium and a 3-day long focus workshop. The
symposium was aimed at theorists, with two 1.5-hour time slots for two talks per day in the morning and a free
discussion time in the afternoon.

The 3-week period has given the participants enough time to interact with each other in a meaningful way, without
time pressure and limits typical for discussions during conventional conferences. The focus workshop aimed at bringing
representatives from the key experimental groups, providing the complementary perspective and the needed balance
between the dreams of theorists and the realities of experimental labs.

The meeting was originally planned for the summer of 2020, but the pandemic forced several postponements, from
2020 to 2021, and from 2021 to 2023, when it was finally held in person. Given the goals of the event, an on-line
format was impossible: a day-to-day human interaction was key to its success.
The uncertainties with scheduling the event have led to several cancellations, but in the end, the meeting has
attracted 66 participants from 17 countries.

Regarding the longer seminar aimed at theoreticians, these included highly visible scientists such as Prof. A.
Landsman (Ohio State University), Prof. O. Smirnova (MBI, Germany), Prof. M. A. Porras (TU Madrid, Spain),
Prof. Y. Murakami (RIKEN, Japan), Prof. K. Ishikawa (U of Tokyo, Japan), Prof. K. Krajewska (U Warsaw,
Poland), Prof. X-B Bian (CAS China), Prof. L. Plaja (U of Salamanca, Spain), Prof. A. Picon (UAM Madrid,
Spain), Prof. D. Milosevic (U Sarajevo, Bosnia and Herzegovina), Prof. L-Y Peng (U Peking), Prof. Kush Saha
(NISER Bhubaneswar, India), Dr. S. Patchkovskii (MBI, Germany). They were joined by younger but already
well-established scientists such as Prof. J-M Ngoko Djokap (U Nebraska, US), Dr. Maria Richter (MBI, Germany),
Drs. E. Pisanty and M. Khokhlova (King’s College London, UK), Dr. D. Ayuso (Imperial College/ Queen Marry
College, London, UK), Drs. R.E.F. Silva and A. Jimenez-Galan (Materials Science Institute of Madrid, Spain), Dr.
U. Bhattacharya (ICFO, Spain).

The workshop welcomed many very promising ”scientific newcomers”, such as Dr. Hao Liang (Peking U and
MPI PKS), Dr. A. Ordonez (ICFO and Imperial College London), Dr. N. Mayer (MBI), R. Martin-Hernandez
(U Salamanca), N. Rana (IIT Bombay), Dr. G. Brown (MBI), M. Even Tsur (Technion), and E. Bernal Molinero
(Materials Science Institute of Madrid, Spain).

During the focus workshop, the symposium participants were joined by such prominent scientists as Prof. O. Cohen
(Technion, Israel), Prof. J. Burgdoerfer (TU Wien, Austria), Prof. J. Biegert (ICFO, Spain), Prof. T. Morishita (U of2
Electro-Communications, Japan), Prof. M. Lein (U Hannover, Germany), Prof. Th. Fennel (U Rostock, Germany),
Prof. J. Berkadar (U Halle, Germany), Prof. T. Popmintchev (U California San Diego US), Prof. S. Witte (ARCNL,
The Netherlands), Prof. I. Fabrikant (U Nebraska, US), Prof. T. Ruchon (U. Paris-Saclay, France), Prof. F. Mauger
(U Louisiana, US), Prof. G. Paulus (U Jena, Germany), Prof. C. Trallero (U Connecticut, US), Prof. M. Wollenhaupt
(U Oldenburg, Germany), to name but a few.

The symposium participants were unanimous regarding the high quality of talks, with the unhurried pace of the
symposium stimulating detailed and productive discussions. Importantly, all symposium participants spent significant
time at the event, ensuring not only very lively discussions during the talks and in the afternoon, but also the emergence
of new collaborations during the meeting, e.g. between Dr. M. Khokhlova (Kings College, London) and the group
of Prof. G. Dixit (IIT Bombay); Prof. O. Smirnova (MBI) and M. Even Tsur (Technion); Dr. U. Bhattacharya
(ICFO) and Prof. M. Ivanov (MBI); Prof. Kush Saha (NISER Bhubaneswar, India) and Prof. M. Ivanov (MBI);
Prof. L-Y. Peng , Dr. Hao Liang and Prof. O. Smirnova; Prof. S. Witte (ARCNL) and Prof. C. Hern ́andez-Garc ́ıa
(U Salamanca); Prof. Pic ́on (UAM), Prof. L. Plaja (U Salamanca) and Drs. R.E.F. Silva and A. Jimenez-Galan
(Materials Science Institute of Madrid, Spain); Prof. M. A. Porras (TU Madrid) and Prof. C. Hern ́andez-Garc ́ıa (U
Salamanca), among others.

The key scientific questions debated during these discussions were ultrafast nonlinear spectroscopy of topological
and strongly correlated solids, applications of structured light for (i) generation and detection of ultrashort bursts
of XUV light and of very strong magnetic fields, (ii) generation of electron vortices in photo-ionization, and (iii)
generation and detection of ultrafast, enantio-sensitive electron currents in chiral molecules.

Some of the new ideas that have emerged during the workshop include the use of nonlinear optical response for
probing topology of Fermi surfaces, the use of ultrafast light’s topology to unveil electron correlation dynamics in
solids, the use of artificial intelligence to boost strong-field calculations, and the development of new measures of
chirality for applications in photo-electron spectroscopy of chiral matter.

The original vision for this meeting was championed by Prof. A. Starace, who has unfortunately passed away before
the meeting took place. A memorial session in his honour, open to the public, has been held during the meeting. The
session was held in the mixed format, with both in-person and on-line presentations, which gave the opportunity to
friends, colleagues and family of Tony to take part. Tony has been instrumental for all aspects of the meeting, and
his outstanding skills in identifying important topics and bringing people together will always be missed.