Search Results
Femtosecond X-ray diffraction from nanolayered oxides
2010, Von Korff Schmising, C., Harpoeth, A., Zhavoronkov, N., Woerner, M., Elsaesser, T., Bargheer, M., Schmidbauer, M., Vrejoiu, I., Hesse, D., Alexe, M.
Femtosecond X-ray scattering offers the opportunity to investigate reversible lattice dynamics with unprecedented accuracy. We show in a prototype experiment how strain propagation modifies the functionality of a ferroelectric system on its intrinsic time scale.
Phonon driven charge dynamics in polycrystalline acetylsalicylic acid mapped by ultrafast x-ray diffraction
2019, Hauf, Christoph, Hernandez Salvador, Antonio-Andres, Holtz, Marcel, Woerner, Michael, Elsaesser, Thomas
The coupled lattice and charge dynamics induced by phonon excitation in polycrystalline acetylsalicylic acid (aspirin) are mapped by femtosecond x-ray powder diffraction. The hybrid-mode character of the 0.9 ± 0.1 THz methyl rotation in the aspirin molecules is evident from collective charge relocations over distances of some 100 pm, much larger than the sub-picometer nuclear displacements. Oscillatory charge relocations around the methyl group generate a torque on the latter, thus coupling electronic and nuclear motions.
Nanoplasmonic electron acceleration in silver clusters studied by angular-resolved electron spectroscopy
2012, Passig, J., Irsig, R., Truong, N.X., Fennel, T., Tiggesbäumker, J., Meiwes-Broer, K.H.
The nanoplasmonic field enhancement effects in the energetic electron emission from few-nm-sized silver clusters exposed to intense femtosecond dual pulses are investigated by high-resolution double differential electron spectroscopy. For moderate laser intensities of 10 14Wcm -2, the delaydependent and angular-resolved electron spectra show laser-aligned emission of electrons up to keV kinetic energies, exceeding the ponderomotive potential by two orders of magnitude. The importance of the nanoplasmonic field enhancement due to resonant Mie-plasmon excitation observed for optimal pulse delays is investigated by a direct comparison with molecular dynamics results. The excellent agreement of the key signatures in the delay-dependent and angular-resolved spectra with simulation results allows for a quantitative analysis of the laser and plasmonic contributions to the acceleration process. The extracted field enhancement at resonance verifies the dominance of surfaceplasmon-assisted re-scattering.
Sub-cycle valleytronics: control of valley polarization using few-cycle linearly polarized pulses
2021, Jiménez-Galán, Álvaro, Silva, Rui E. F., Smirnova, Olga, Ivanov, Misha
So far, it has been assumed that selective excitation of a desired valley in the Brillouin zone of a hexagonal two-dimensional material has to rely on using circularly polarized fields. We theoretically demonstrate a way to control the valley excitation in hexagonal 2D materials on a few-femtosecond timescale using a few-cycle, linearly polarized pulse with controlled carrier–envelope phase. The valley polarization is mapped onto the strength of the perpendicular harmonic signal of a weak, linearly polarized pulse, which allows to read this information all-optically without destroying the valley state and without relying on the Berry curvature, making our approach potentially applicable to inversion-symmetric materials. We show applicability of this method to hexagonal boron nitride and MoS2.