Light-wave driven charge- and spin dynamics
University of Technology Graz, Austria
Abstract: Ultrafast coherent electron and spin dynamics in solids In electronics, functionality is achieved by switching between electronic states of matter by applying external electric or magnetic fields. Strong couplings in-between charge carriers and to the crystal lattice conspire to randomize energies and momenta extremely fast and efficiently, leaving little room for coherent manipulation. However, the prospects of coherent control protocols as demonstrated in isolated atomic systems are alluring and contemporary ultrafast laser sources might be a new ingredient to overcome this entrapment. This talk will discuss two experiments demonstrating that single cycle optical fields at optical frequencies allow manipulating electronic and spin degrees of freedom in solid state systems at optical clock rates faster than de-coherence. Ultrafast bidirectional energy transfer between a light-field and the band-structure of silica proves the early times reversibility of electronic excitations and holds promise of novel ultrafast, coherent optoelectronic applications1. As a corollary of this ultrafast coherent modification of the electronic system, in suitably chosen herterostructures also the spin system can be manipulated coherently. Optically induced spin transfer is demonstrated as a route to the direct, all-optical manipulation of macroscopic magnetic moments on previously inaccessible attosecond timescales2. 1. Sommer, A. et al. Attosecond nonlinear polarization and light–matter energy transfer in solids. Nature 534, 86–90 (2016). 2. Siegrist, F. et al. Light-wave dynamic control of magnetism. Nature 571, 240–244 (2019).
Biography: PhD on Delay in Photoemission at LMU Munich, Germany. Postdoc at Max-Planck Institute of Quantum Optics, Germany and the UC Berkely, USA on attosecond spectroscopy in condensed phase systems. Since 2019 professor of physics and head of the institute of experimental physics at the Technical University Graz, Austria. Research activities centered around the exploration of ultrafast light-wave manipulation of electronic and spin degrees of freedom in solid-state systems.
High-energy mid-infrared femtosecond pulses for attosecond science
Eiji J. Takahashi
Abstract: Since the first demonstration of isolated attosecond pulses in 2001, attosecond science has emerged as an important frontier research area of ultrafast phenomena. However, one critical bottleneck in the progress of research studying attosecond phenomena is the limited pulse energy of attosecond pulses. In this talk, I will introduce our two novel laser systems to drive high-energy attosecond pulses: one is 50-mJ 3-channel waveform synthesizer consisting of pulses with near-infrared and mid-infrared wavelengths, and the other is a multi-TW mid-infrared laser system via dual-chirped optical parametric amplification (DC-OPA).
Biography: Eiji J. Takahashi is a Senior Research Scientist at RIKEN Center for Advanced Photonics. After receiving his Ph.D degree in 2001, he contributed to the early development of intense high-order harmonic sources and spectroscopy in RIKEN. In 2004, he joined the Institute for Molecular Science, Okazaki, Japan, where he was an Assistant Professor. Since re-joining RIKEN in 2006, he is a member of the Attosecond Science Research Team. Currently, he is mainly focusing on the energy scaling of isolated attosecond pulses up to gigawatt-scale and the development high-energy MIR laser system based on DC-OPA. His research interests include high-intensity laser-matter interactions, the generation of coherent soft-x-ray/XUV pulses, attosecond science, and high-power laser technology including an optical waveform synthesizer.