A5076282922- Magnetic properties of thin films
- Quantum and electron transport phenomena
- Molecular Junctions and Nanostructures
- Heusler alloys: electronic and magnetic properties
- Magneto-Optical Properties and Applications
- 2D Materials and Applications
- Organic Light-Emitting Diodes Research
- Topological Materials and Phenomena
- Physics of Superconductivity and Magnetism
- Surface and Thin Film Phenomena
- Semiconductor materials and devices
- Graphene research and applications
- Advanced Electron Microscopy Techniques and Applications
- Organic Electronics and Photovoltaics
- Porphyrin and Phthalocyanine Chemistry
- Magnetic Properties and Applications
- Magnetic and transport properties of perovskites and related materials
- Advanced Memory and Neural Computing
- Surface Chemistry and Catalysis
- Advanced Chemical Physics Studies
- ZnO doping and properties
- Laser-Matter Interactions and Applications
- Magnetism in coordination complexes
- Mechanical and Optical Resonators
- MXene and MAX Phase Materials
TU Dortmund University
2016-2025
University of Cambridge
2021
University of Leeds
2021
Lancaster University
2021
University of Kaiserslautern
2008-2017
Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau
2013
Uppsala University
2010
Paul Scherrer Institute
2010
Johannes Gutenberg University Mainz
2003-2006
National University of Ireland, Maynooth
2001
The interplay of light and magnetism has been a topic interest since the original observations Faraday Kerr where magnetic materials affect polarization. While these effects have historically exploited to use as probe there is increasing research on using polarized alter or manipulate magnetism. For instance deterministic switching without any applied fields laser pulses circular observed for specific ferrimagnetic materials. Here we demonstrate, first time, optical control ferromagnetic...
Gold surfaces host special electronic states that have been understood as a prototype of Shockley surface (SSs). These SSs are commonly employed to benchmark the capability angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy. We find these can be reinterpreted topologically derived (TDSSs) topological insulator (TI), recently discovered quantum state. Based on band structure calculations, Z2 invariant well defined characterize nontrivial features gold we...
We consider an $\stackrel{\ensuremath{\rightarrow}}{N}M$ quantum cloning transformation acting on pure two-level states lying the equator of Bloch sphere. An upper bound for its fidelity is presented, by establishing a connection between optimal phase-covariant and phase estimation. give explicit form that achieves case $N=1,$ $M=2,$ find link this eavesdropping in cryptographic scheme BB84.
There is a recent interest in nanoscale materials, particular, nanotubes based not only on carbon. In this study, photoemission spectra of single MoS2 deposited Si surface were recorded order to explain their electronic structure. The photoelectrons excited by femtosecond laser oscillator resulting two-photon photoemission. A spectromicroscopic technique imaging time-of-flight detection was used record the spatially resolved photoelectron spectra. Self-consistent structure calculations for...
The Elliott-Yafet (EY) mechanism is arguably the most promising candidate to explain light-induced ultrafast demagnetization dynamics in ferromagnetic transition metals on time scales order of 100 fs. So far, only electron-phonon (or impurity) scattering has been analyzed as process needed account for demagnetization. We show that an EY-like based electron-electron potential time-resolved magneto-optical Kerr effect measurements thin magnetic Co and Ni films, without reference a ``phononic...
A comprehensive set of magneto-optical experiments on ferromagnetic nickel combined with theoretical modeling points to a single microscopic mechanism for laser-induced femtosecond-scale demagnetization.
The evolution of the electronic band structure simple ferromagnets Fe, Co, and Ni during their well-known ferromagnetic-paramagnetic phase transition has been under debate for decades, with no clear even contradicting experimental observations so far. Using time- spin-resolved photoelectron spectroscopy, we can make a movie on how properties change in real time after excitation an ultrashort laser pulse. This allows us to monitor large transient changes cobalt first time. We show that loss...
Motivated by the recent controversy about importance of spin-flip scattering for ultrafast demagnetization in ferromagnets, we study spin-dependent electron dynamics based on a dynamical Elliott-Yafet mechanism. The key improvement to earlier approaches is use modified Stoner model with dynamic exchange splitting between majority and minority bands. In framework our microscopic model, find novel feedback effect time-dependent scattering. This allows us reproduce important properties...
Magnetization reversal using circularly polarized light provides a way to control magnetization without any external magnetic field and has the potential revolutionize data storage. However, in order reach ultra-high density storage, high anisotropy media providing thermal stability are needed. Here, we evidence all-optical switching for different TbxCo1−x ferrimagnetic alloy compositions fs- ps-laser pulses demonstrate films with fields reaching 6 T corresponding constants of 3 × 106...
We reveal that optical excitation of heterogeneous materials by ultrashort light pulses induces ultrafast intersite spin transfer.
Altermagnetic (AM) materials exhibit non-relativistic, momentum-dependent spin-split states, ushering in new opportunities for spin electronic devices. While the characteristics of spin-splitting are documented within framework non-relativistic group symmetry, there is limited exploration inclusion relativistic symmetry and its impact on emergence a novel band structure. This study delves into intricate structure an AM material, α-MnTe. Employing temperature-dependent angle-resolved...
Time-resolved momentum microscopy is an emerging technique based on photoelectron spectroscopy for characterizing ultrafast electron dynamics and the out-of-equilibrium electronic structure of materials in entire Brillouin zone with high efficiency. In this article, we introduce a setup time-resolved energy-filtered microscope coupled to custom-made high-harmonic generation photon source driven by multi-100 kHz commercial Yb-ultrafast laser that delivers fs pulses extreme ultraviolet range....
The femtosecond magnetization dynamics of a thin cobalt film excited with ultrashort laser pulses has been studied using two complementary pump-probe techniques, namely, spin-, energy-, and time-resolved photoemission the magneto-optical Kerr effect. Combining methods, it is possible to identify microscopic electron spin-flip mechanisms responsible for ultrafast macroscopic film. In particular, we show that electron-magnon excitation does not affect overall even though an efficient channel...
Photoemission electron microscopy was used to image the electrons photoemitted from specially tailored Ag nanoparticles deposited on a Si substrate (with its native oxide ${\mathrm{SiO}}_{x}$). induced by illumination with Hg UV lamp (photon energy cutoff $\ensuremath{\hbar}{\ensuremath{\omega}}_{\mathrm{UV}}=5.0\text{ }\text{ }\mathrm{eV}$, wavelength ${\ensuremath{\lambda}}_{\mathrm{UV}}=250\text{ }\mathrm{nm}$) and Ti:sapphire femtosecond laser...
We have grown thin films of the Heusler compound ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}$ by RF magnetron sputtering. On (100)-oriented MgO substrates we find fully epitaxial and $L{2}_{1}$ ordered growth. ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}(11\overline{2}0)$ substrates, film growth is (110)-oriented, several in-plane domains are observed. The temperature dependence electrical resistivity shows a power law with an exponent $7∕2$ at low temperatures. Investigation bulk magnetic properties...
In order to explore the role of enhanced spin-orbit interactions on laser-induced ultrafast magnetization dynamics, we performed a comparative study cobalt thin films and Co/Pt multilayers. We show that presence interfaces gives rise three-fold faster demagnetization upon femtosecond laser heating. Experimental data for wide range fluences are analyzed using Microscopic 3-Temperature Model. find Elliott-Yafet spin-flip scattering in multilayer structure is increased by at least factor four...
We investigate femtosecond spin injection from an optically excited Ni top layer into Au bottom using time-resolved complex magneto-optical Kerr effect (C-MOKE) measurements. Employing the C-MOKE formalism, we are able to follow layer-resolved demagnetization in and simultaneous adjacent film, both occurring within $\ensuremath{\sim}40\phantom{\rule{0.16em}{0ex}}\mathrm{fs}$. confirm ballistic diffusive propagation of transfer process with ab initio theory superdiffusive transport...
Spin filtering at organic-metal interfaces is often determined by the details of interaction between organic molecules and inorganic magnets used as electrodes. Here we demonstrate a spin-filtering mechanism based on dynamical spin relaxation long-living interface states formed magnet weakly physisorbed molecules. We investigate case Alq3 Co and, combining two-photon photoemission experiments with electronic structure theory, show that observed long-time spin-dependent electron dynamics...
Coherent THz optical lattice and hybridized phonon-magnon modes are triggered by femtosecond laser pulses in the antiferromagnetic van der Waals semiconductor FePS