Scientific program

In the condensed matter as in isolated systems, at the shortest timescale of a few femtoseconds, the electronic and nuclear motions are decoupled. At intermediate timescale of a few 10 fs to 100 fs, excited electrons and electron-hole pairs (exciton) couple to the lattice which starts moving (phonons) and adiabatically acts in turn on the electronic density.

Dynamical processes involving solely electronic motion and strongly depending on electron-electron correlation are extremely rich. They include the electronic and electron-hole transport or current, responsible for conductivity and superconductivity which can be studied in real time, charge screening on surfaces, collective processes such as plasmons. In particular, studies in ATTOLAB focus on the current dynamics of the so-called Dirac fermions in topological insulators (material which is conductor at surface and insulator in the bulk) [Hajlaoui12, Hajlaoui14, Cacho15]. Attention is also paid to multi-ferroic materials, e.g., oxides, which simultaneously present ferroic (permanent electric moment) and magnetic (permanent magnetic moment) properties, where one studies the ultrafast switching of the either electric or magnetic polarization under an external field [Rault13, Rault14]. Multi-ferroics are promising materials for applications.

The interaction of light with solid matter covers a large range of fundamental processes which are also relevant for applications. Most of them are addressed in time-resolved studies:

• As in isolated systems, attosecond time-resolved studies access photoemission delays in solid, that is the time of the order of a few ten attoseconds necessary for an electron to leave the solid after instantaneous absorption of photons from an ultra-short light pulse hitting the surface [Cavalieri07].

• The interaction of a dielectric solid with a strong laser field is of fundamental as well as practical interest. For example, the excited electrons in the conduction band relax their energy through various processes which may end into “optical breaking” that causes irreversible damage : this situation is met in optical elements of any high power laser chain [Guizard15]. The full understanding and possible remediation of optical breakdown requires time-resolved study of electronic relaxation. Moreover, a strong laser field can drive an electron current across the gap of an insulator or semi-conductor, making it possible the ultrafast control of a transistor [Krüger11, Schultze13].

• Nanoplasmonic, that is the excitation and manipulation of coupled electronic density waves and electromagnetic waves at the metal/dielectric interface, currently exploit unique properties of surface plasmons and polaritons, e.g., field enhancement, light confinement and guiding [Polman05, Stockman07]. They find applications spanning (bio-)sensing, solid-state lighting, optical storage, interconnects and waveguides [Polman2005], where ultrafast dynamics of plasmons should play an increasing role.

• The time-resolved studies of chemical reactivity and catalytic processes on surfaces constitute an important extension of the reactivity studies in the gas phase.

• Spin and magnetization dynamics.

• Phonons dynamics.

Experimental techniques

• ARPES
• PEEM
• Spin-resolved electron spectroscopy
• Coherent diffraction Imaging
• Spectral interferometry