A5029019353- Electronic and Structural Properties of Oxides
- Organic and Molecular Conductors Research
- Magnetic and transport properties of perovskites and related materials
- Multiferroics and related materials
- Advanced Electron Microscopy Techniques and Applications
- Physics of Superconductivity and Magnetism
- Advanced X-ray Imaging Techniques
- Metal-Catalyzed Oxygenation Mechanisms
- Rare-earth and actinide compounds
- Ferroelectric and Piezoelectric Materials
- Magnetic properties of thin films
- Advanced Condensed Matter Physics
- Electron and X-Ray Spectroscopy Techniques
- Advanced Chemical Physics Studies
- Iron-based superconductors research
- X-ray Spectroscopy and Fluorescence Analysis
- Particle Accelerators and Free-Electron Lasers
- Photorefractive and Nonlinear Optics
- Educational Challenges and Innovations
- Radioactive Decay and Measurement Techniques
- Laser-Matter Interactions and Applications
- Shape Memory Alloy Transformations
- Gyrotron and Vacuum Electronics Research
- CO2 Reduction Techniques and Catalysts
- Topological Materials and Phenomena
ETH Zurich
2015-2024
Paul Scherrer Institute
2013-2019
Swiss Light Source
2014-2019
University of Pennsylvania
2016
SLAC National Accelerator Laboratory
2016
Stanford Synchrotron Radiation Lightsource
2016
Max Planck Institute for Biophysical Chemistry
2010-2015
University of Zurich
2013
Max Planck Society
2010-2013
Slovenské Elektrárne (Slovakia)
2002
Multiferroics have attracted strong interest for potential applications where electric fields control magnetic order. The ultimate speed of via magnetoelectric coupling, however, remains largely unexplored. Here, we report an experiment in which drove spin dynamics multiferroic TbMnO3 with intense few-cycle terahertz (THz) light pulse tuned to resonance electromagnon, electric-dipole active excitation. We observed the resulting motion using time-resolved resonant soft x-ray diffraction. Our...
Using femtosecond time-resolved x-ray diffraction, we directly monitor the coherent lattice dynamics through an ultrafast charge-density-wave-to-metal transition in prototypical Peierls system ${\mathrm{K}}_{0.3}{\mathrm{MoO}}_{3}$ over a wide range of relevant excitation fluences. While low fluence regime follow structural associated with collective amplitude mode; for fluences above melting threshold electronic density modulation observe transient recovery periodic distortion. We can...
Femtosecond time-resolved X-ray diffraction is used to study a photo-induced phase transition between two charge density wave (CDW) states in 1T-TaS$_2$, namely the nearly commensurate (NC) and incommensurate (I) CDW states. Structural modulations associated with NC-CDW order are found disappear within 400 fs. The I-CDW then develops through nucleation/growth process which ends 100 ps after laser excitation. We demonstrate that newly formed fragmented into several nanometric domains growing...
Abstract Transition metal oxides are among the most promising solar materials, whose properties rely on generation, transport and trapping of charge carriers (electrons holes). Identifying latter’s dynamics at room temperature requires tools that combine elemental structural sensitivity, with atomic scale resolution time (femtoseconds, fs). Here, we use fs Ti K-edge X-ray absorption spectroscopy (XAS) upon 3.49 eV (355 nm) excitation aqueous colloidal anatase titanium dioxide nanoparticles...
We utilized femtosecond time-resolved resonant inelastic X-ray scattering and ab initio theory to study the transient electronic structure photoinduced molecular dynamics of a model metal carbonyl photocatalyst Fe(CO)5 in ethanol solution. propose mechanistic explanation for parallel ultrafast intra-molecular spin crossover ligation Fe(CO)4 which are observed following charge transfer photoexcitation as reported our previous [Wernet et al., Nature 520, 78 (2015)]. find that branching...
Using femtosecond time-resolved x-ray diffraction we investigate the structural dynamics of coherently excited A1g phonon mode in Fe-pnictide parent compound BaFe2As2. The fluence dependent intensity oscillations two specific Bragg reflections with distinctly different sensitivity to pnictogen height allow us quantify coherent modifications Fe-As tetrahedra, indicating a transient increase Fe magnetic moments. By comparison photoemission data derive electron-phonon deformation potential for...
We performed ultrafast time-resolved near-infrared pump, resonant soft x-ray diffraction probe measurements to investigate the coupling between photoexcited electronic system and spin cycloid magnetic order in multiferroic $\mathrm{TbMn}{\mathrm{O}}_{3}$ at low temperatures. observe melting of long range antiferromagnetic excitation fluences with a decay time constant $22.3\ifmmode\pm\else\textpm\fi{}1.1\phantom{\rule{0.16em}{0ex}}\mathrm{ps}$, which is much slower than \ensuremath{\sim}1 ps...
The ultrafast dynamics of the octahedral rotation in $\mathrm{Ca}:\mathrm{SrTi}{\mathrm{O}}_{3}$ is studied by time-resolved x-ray diffraction after photoexcitation over band gap. By monitoring intensity a superlattice reflection that directly related to structural order parameter soft-mode driven antiferrodistortive phase $\mathrm{Ca}:\mathrm{SrTi}{\mathrm{O}}_{3}$, we observe an relaxation on 0.2 ps timescale oxygen octahedron, which found be independent initial temperature despite large...
The strength of the electron-phonon coupling parameter and its evolution throughout a solid's phase diagram often determines phenomena such as superconductivity, charge- spin-density waves. Its experimental determination relies on ability to distinguish thermally activated phonons from those emitted by conduction band electrons, which can be achieved in an elegant way ultrafast techniques. Separating electronic out-of-equilibrium lattice subsystems, we probed their re-equilibration...
Magnetic shape memory Heusler alloys are multiferroics stabilized by the correlations between electronic, magnetic and structural order. To study these we use time resolved x-ray diffraction magneto-optical Kerr effect experiments to measure laser induced dynamics in a alloy Ni$_2$MnGa film reveal set of timescales intrinsic system. We observe coherent phonon which identify as amplitudon modulated structure an ultrafast phase transition leading quenching incommensurate modulation within...
Femtosecond time-resolved x-ray diffraction is employed to study the dynamics of periodic lattice distortion (PLD) associated with charge-density-wave (CDW) in K0.3MoO3. Using a multi-pulse scheme we show ability extend lifetime coherent oscillations PLD about undistorted structure through re-excitation electronic states. This suggests that it possible enter regime where symmetry potential energy landscape corresponds high phase but scattering pathways lead damping are still controllable by...
Intense, few-cycle pulses in the terahertz frequency range have strong potential for schemes of control over vibrational modes solid-state materials electronic ground-state. Here we report an experiment using single cycle to directly excite lattice vibrations ferroelectric material $\mathrm{Sn_2P_2S_6}$ and ultrafast x-ray diffraction quantify resulting structural dynamics. A model a damped harmonic oscillator driven by transient electric field describes well movement Sn$^{2+}$ ion along...
In this paper we present a development of multipurpose vacuum chamber which primal function is to be used in pump/probe experiments with free electron laser (FEL) radiation. The constructed for serial diffraction and spectroscopy allowing fast exchange samples during the measurement process. For samples, liquid jet systems are used. Both applications, utilizing soft x-ray FEL pulses as pump optical probe vice versa documented. Experiments solid well presented. When working jets, system...
Using femtosecond time-resolved hard x-ray diffraction, we investigate the structural dynamics of orthorhombic distortion in Fe-pnictide parent compound BaFe2As2. The analyzed by transient splitting (1 0 3) Bragg reflection is suppressed on an initial timescale 35 ps, which much slower than suppression magnetic and nematic order. This observation demonstrates a state with persistent magnetic/nematic order are strongly linked thermal equilibrium. We suggest way quantifying coupling between...
It is expected that free-electron laser (FEL) radiation with its unique properties will allow real-time tracking of structural changes during chemical reactions. The methods suggested being applied range from x-ray spectroscopy to diffraction. In order reach this goal, in work we present our studies utilizing soft FEL generated at the FLASH facility. We case ultrafast diffraction on nanocrystalline lamellar assemblies relevance and heat dissipation polymer foils (upon excitation) as revealed...
We determine the pathways in photo-dissociation reactions of Fe(CO)5 both gas phase and solution by mapping valence electronic structure reaction intermediates with femtosecond X-ray laser spectroscopy.
We have studied the ultrafast changes of electronic states in bulk ZnO upon intense hard x-ray excitation from a free electron laser. By monitoring transient anisotropy induced an optical probe beam, we observe delayed breaking initial c-plane symmetry crystal that lasts for several picoseconds. Interaction with pulses modifies state filling manner inconsistent simple increase temperature. These results may indicate way to use ultrashort investigate high-energy carrier dynamics and control...
We photoexcite SrTiO 3 and EuTiO in their purely soft-mode-driven structurally distorted phase trace the structural order parameter via ultra-short x-rays. observe a rapid decay for an intriguing transient enhancement EuTiO3.