This Faraday discussion will be a hybrid event, allowing participation both in person and online.
Welcome
Join us in London or online in May 2022 for this edition of the Faraday Discussion series. For over 100 years and 300 meetings, Faraday Discussions have been the forefront of physical chemistry. Many of these Discussions have become landmark meetings in their field.This meeting is for established scientists, post-graduate students and industrial researchers interested in ultrafast control of the physical properties of materials by light excitation and/or THz excitation. Given the rapid development of experimental techniques, including XFEL science, THz science and various pump–probe techniques, and developments in the theory of ultrafast, out-of-equilibrium and multiscale processes driven by light or THz excitation, this meeting will provide a roadmap of where the field is and what the challenges are over the next 5–10 years and beyond.
The unique format of the Faraday Discussions will allow for in-depth discussions, which will stimulate new thoughts and define new horizons, and opportunities to establish new collaborations. An important aspect in the discussions will be the complementarity of experimental materials scientists and theoreticians for designing new ways to control materials or understanding transformation processes.
On behalf of the organising committee, we look forward to welcoming you to London, or if you are joining us virtually, online.
Eric Collet
Chair
Format
Faraday Discussions remain amongst the only conferences to distribute the speakers’ research papers in advance, allowing the majority of each meeting to be devoted to discussion in which all delegates can participate. Following each meeting a written record of the discussion is published alongside the papers in the Faraday Discussions journal.Find out more about the Faraday Discussions in the video available.
Themes
Ultrafast science has been for long limited to the investigation of molecular processes. Over the past 10 years, investigation of ultrafast processes has expanded to material science, with specific aspects related to solid-state like excitation of electrons in band structures, collective phonon excitation, or specific probes for electronic and structural reorganization such as X-ray diffraction or ARPES.The Faraday Discussion will be organised into the following themes:
Materials science: ultrafast transformation, electron-phonon coupling, multi-scale aspects
Ultrafast phenomena in materials, induced by ultrashort light excitation, are driven by the subtle coupling between electronic and structural degrees of freedom, which is at the origin of the emergence of functions. These functions can be triggered by direct or indirect excitation of various degrees of freedom, such as spin, electron, phonon, and lattice. These ultrafast phenomena concern various materials, from hard-condensed matter to molecular materials, and various properties such as conductivity, magnetism and ferroelectricity. However, the complex out-of-equilibrium dynamics induced by light in these diverse systems show common features at the origin of the emergence of functions, such as the coupling between different sub-systems that are multi-scale in space and time. This session will illustrate the diversity of ultrafast processes in materials science, while looking for universality in their description, understanding and control.
Theory of out of equilibrium light-induced phenomena
Molecular transformations, at the heart of chemistry and emergence of functions, involve subtle and coupled changes of electronic and nuclear configurations. This is also true for photoinduced phase transition in materials. When induced by light, these electronic and structural reorganizations can be extremely fast and coupled. Providing a relevant picture of the transformation process is necessary for developing light-activated functions. This session will discuss the challenges faced by both theoreticians and experimentalists in understanding electron-phonon coupling, conical intersection, which may occur beyond the Born–Oppenheimer approximation. This breakdown of the Born–Oppenheimer approximation is the basis of significant research interest in both fundamental and applied fields related to non-adiabatic phenomena.
Optical excitation processes
Under light pulse excitation, remarkable molecular processes can emerge, and in the solid state, ultrafast photoinduced phase transitions (PIPT) represent a fascinating route beyond femtochemistry. The PIPT field has developed around two main lines; delocalized photoexcitation in itinerant electron materials, and localized molecular excitation. Enormous progress has been achieved in the description of ultrafast processes, with the intensive development of ultrafast optical, electron or X-ray experiments, opening completely new possibilities for the real time probing of these processes. This session will be devoted to the development of PIPT concepts, which are now vividly exploited in condensed matter, for driving phase transitions on the timescale of a phonon period.
THz and laser field excitation processes
New laser-based technologies promise control of elementary electronic and structural processes in transforming matter on the femtosecond timescale (1 fs = 10-15 s). In this session, we will discuss taking steps towards an unprecedented degree of control over material functionality. We will also discuss how nonlinear phononics represents a new method for triggering structural dynamics, and how new excitation processes are able to transform materials in the ground state, thus promising capabilities overpassing optical excitation, through more selective and directive processes.
