A5002559554- Topological Materials and Phenomena
- Advanced Condensed Matter Physics
- Graphene research and applications
- 2D Materials and Applications
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Magnetic properties of thin films
- Particle Accelerators and Free-Electron Lasers
- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Magnetic and transport properties of perovskites and related materials
- Advanced X-ray Imaging Techniques
- Quantum and electron transport phenomena
- GaN-based semiconductor devices and materials
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Electron Microscopy Techniques and Applications
- Physics of Superconductivity and Magnetism
- Machine Learning in Materials Science
- ZnO doping and properties
- Rare-earth and actinide compounds
- Ga2O3 and related materials
- Magnetic Field Sensors Techniques
- Chalcogenide Semiconductor Thin Films
- Photocathodes and Microchannel Plates
- Phase-change materials and chalcogenides
Forschungszentrum Jülich
2016-2025
RWTH Aachen University
2023-2025
Jülich Aachen Research Alliance
2011-2023
University of Duisburg-Essen
2013-2022
Grunberger Diabetes Institute
2021
Ernst Ruska Centre
2011-2020
Poznań University of Technology
2017
University of Connecticut
2006-2009
Boston University
2005-2008
Lawrence Berkeley National Laboratory
2008
We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed gain (approximately 3000) and radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, intensity fluctuations, are all consistent with models for SASE FELs.
Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring bunch charge distribution. A complete characterization linear and nonlinear modes SASE FEL operation was performed. At saturation produces (30-100 fs FWHM) with a peak power GW level full transverse coherence. wavelength tuned range 95-105 nm.
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...
We report on the observation of photogalvanic effects in epitaxially grown Sb2Te3 and Bi2Te3 three-dimensional (3D) topological insulators (TI). show that asymmetric scattering Dirac fermions driven back forth by terahertz electric field results a dc current. Because "symmetry filtration" current is generated surface electrons only provides an optoelectronic access to probe electron transport TI, domains orientation, details 3D TI even at room temperature.
3D topological insulators are a new state of quantum matter which exhibits both bulk band structure with an insulating energy gap as well metallic spin-polarized Dirac fermion states when interfaced topologically trivial material. There have been various attempts to tune the point desired energetic position for exploring its unusual properties. Here we show direct experimental proof by angle-resolved photoemission realization vertical p-n junction made heterostructure two different binary TI...
A combined theoretical and experimental study reveals evidence for the dual topological insulating character of stoichiometric natural superlattice phase $\mathrm{Bi_{1}Te_{1}}=\mathrm{[Bi_{2}]_{1}[Bi_{2}Te_{3}]_{2}}$, being a stack alternating Bi bilayers two quintuple layers $\mathrm{Bi_{2}Te_{3}}$. We identify $\mathrm{Bi_{1}Te_{1}}$ by density functional theory to exhibit non trivial time-reversal symmetry-driven $\mathbb{Z}_{2}=(0;001)$ additionally mirror-symmetry induced mirror Chern...
We report on the observation of a terahertz radiation induced photon drag effect in epitaxially grown $n$- and $p$-type (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$ three dimensional topological insulators with different antimony concentrations $x$ varying from 0 to 1. demonstrate that excitation polarized results $dc$ electric photocurrent. While at normal incidence current arises due photogalvanic surface states, oblique it is outweighed by trigonal effect. The developed microscopic model theory...
ReS$_2$ is considered as a promising candidate for novel electronic and sensor applications. The low crystal symmetry of the van der Waals compound leads to highly anisotropic optical, vibrational, transport behavior. However, details band structure this fascinating material are still largely unexplored. We present momentum-resolved study monolayer, bilayer, bulk using k-space photoemission microscopy in combination with first-principles calculations. demonstrate that valence electrons -...
We present a theory of temperature-dependent photoemission which accurately describes phonon effects in soft and hard x-ray angle-resolved photoemission. Our approach is based on fully relativistic one-step that quantitatively reproduces the phonon-assisted transitions beyond usual $\mathbf{k}$-conserving dipole selection rules lead to so-called XPS limit and/or high temperature regime. Vibrational atomic displacements have been included using coherent potential approximation analogy...
The structural perfection of the topological insulator (TI) Bi2Te3 is a key issue for its employment in future device applications. State art TIs, featuring exotic electronic properties, predominantly suffer from defects such as twin domains. A suppression domains molecular beam epitaxy-grown thin films on Si(111) substrates—measured by X-ray diffraction pole figure scans—is presented this paper. numerical analysis van der Waals potentials was performed, revealing nucleation collinear with...
The interfaces between two condensed phases often exhibit emergent physical properties that can lead to new physics and novel device applications are the subject of intense study in many disciplines. We here apply experimental theoretical techniques characterization one such interesting interface system: two-dimensional electron gas (2DEG) formed multilayers consisting $\mathrm{SrTi}{\mathrm{O}}_{3}$ (STO) $\mathrm{GdTi}{\mathrm{O}}_{3}$ (GTO). This system has been multiple studies recently...
For quasi-freestanding 2H-TaS2 in monolayer thickness grown by situ molecular beam epitaxy on graphene Ir(111), we find unambiguous evidence for a charge density wave close to 3 × periodicity. Using scanning tunneling spectroscopy, determine the magnitude of partial gap. Angle-resolved photoemission complemented spectroscopy unoccupied states, makes tight-binding fit band structure TaS2 possible. As hybridization with substrate bands is absent, yields precise value doping layer. Additional...
The concepts of Weyl fermions and topological semimetals emerging in three-dimensional momentum space are extensively explored owing to the vast variety exotic properties that they give rise to. On other hand, very little is known about semimetallic states two-dimensional magnetic materials, which present foundation for both future information technology. Here, we demonstrate including magnetization direction into analysis allows a natural classification manifest ferromagnets as result...
Dirac-like dispersion in topological surface states is strongly perturbed by hybridization with valence-band for Bi${}_{2}$Te${}_{3}$-terminated surfaces, but remains preserved MnBi${}_{2}$Te${}_{4}$-terminated surfaces.
Electron accumulation states in InN have been measured using high resolution angle-resolved photoemission spectroscopy (ARPES). The electrons the layer discovered to reside quantum well states. ARPES was also used measure Fermi surface of these states, as their constant binding energy contours below level ${E}_{F}$. and size for could be controlled by varying method preparation. This is first unambiguous observation that are quantized time associated with such has measured.
The unique properties of synchrotron radiation, such as broad energy spectrum, variable light polarization, and flexible time structure, have made it an enormously powerful tool in the study magnetic phenomena materials. refinement experimental techniques has led to many new research opportunities, keeping up with challenges put by modern magnetism research. In this contribution, we review some recent developments application radiation particularly soft X-rays current problems magnetism,...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation L. Plucinski, G. Mussler, J. Krumrain, A. Herdt, S. Suga, D. Grützmacher, C. M. Schneider; Robust surface electronic properties of topological insulators: Bi2Te3 films grown by molecular beam epitaxy. Appl. Phys. Lett. 30 May 2011; 98 (22): 222503. https://doi.org/10.1063/1.3595309 Download citation file: Ris...