A5072185721- Topological Materials and Phenomena
- Graphene research and applications
- Advanced Condensed Matter Physics
- 2D Materials and Applications
- Electronic and Structural Properties of Oxides
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- ZnO doping and properties
- Copper-based nanomaterials and applications
- Optical Coherence Tomography Applications
- Magnetic properties of thin films
- Photonic and Optical Devices
- Electron and X-Ray Spectroscopy Techniques
- Photonic Crystals and Applications
- Magnetic and transport properties of perovskites and related materials
- Quantum Dots Synthesis And Properties
- Digital Holography and Microscopy
- Microfluidic and Bio-sensing Technologies
- Orbital Angular Momentum in Optics
- Chalcogenide Semiconductor Thin Films
- Organic and Molecular Conductors Research
- Electrocatalysts for Energy Conversion
- High-pressure geophysics and materials
- MXene and MAX Phase Materials
- Photovoltaic Systems and Sustainability
University of Würzburg
2018-2024
École Polytechnique Fédérale de Lausanne
1999-2024
Advanced Light Source
2013-2024
Innsbruck Medical University
2019-2024
Universität Innsbruck
2019-2024
Complexity and Topology in Quantum Matter
2019-2024
Physikalisch-Technische Bundesanstalt
2024
Lawrence Berkeley National Laboratory
2014-2023
Swiss Federal Laboratories for Materials Science and Technology
2023
ETH Zurich
2023
Oxygen vacancies created in anatase TiO(2) by UV photons (80-130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission reveals that the quasiparticles are large polarons. These results indicate can be tuned from insulator to polaron gas weakly correlated metal as function of doping clarify nature conductivity this material.
High-quality single crystals of MnBi2Te4 are grown for the first time by slow cooling within a narrow range between melting points Bi2Te3 (586 °C) and (600 °C). Single-crystal X-ray diffraction electron microscopy reveal ubiquitous antisite defects in both cation sites and, possibly, Mn vacancies (Mn0.85(3)Bi2.10(3)Te4). Thermochemical studies complemented with high-temperature establish limited phase stability metastability at room temperature. Nevertheless, synthesis can be scaled-up as...
Anatase TiO2 is among the most studied materials for light-energy conversion applications, but nature of its fundamental charge excitations still unknown. Yet it crucial to establish whether light absorption creates uncorrelated electron-hole pairs or bound excitons and, in latter case, determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that direct...
The layered van der Waals antiferromagnet MnBi${}_{2}$Te${}_{4}$ has been predicted previously to realize the first intrinsic magnetic topological insulator. Here, authors report spin- and angle-resolved photoemission experiments for MnBi${}_{2}$Te${}_{4}$(0001) surface, revealing a surface state in bulk band gap providing evidence interplay between exchange interaction spin-orbit coupling electronic structure. thus constitutes promising candidate exploit of states order spintronic device concepts.
Magnetic continuum soft robots can actively steer their tip under an external magnetic field, enabling them to effectively navigate in complex vivo environments and perform minimally invasive interventions. However, the geometries functionalities of these robotic tools are limited by inner diameter supporting catheter as well natural orifices access ports human body. Here, we present a class soft-robotic chains (MaSoChains) that self-fold into large assemblies with stable configurations...
Observations of the anomalous Hall effect in RuO2 and MnTe have demonstrated unconventional time-reversal symmetry breaking electronic structure a recently identified new class compensated collinear magnets, dubbed altermagnets. While MnTe, signal accompanied by vanishing magnetization is observable at remanence, excluded for Néel vector pointing along zero-field [001] easy-axis. Guided analysis ab initio calculations, field-induced reorientation from easy-axis toward [110] hard-axis was...
Abstract Altermagnets are a novel class of magnetic materials, where order is staggered both in coordinate and momentum space. The metallic rutile oxide RuO 2 , long believed to be textbook Pauli paramagnet, recently emerged as putative workhorse altermagnet when resonant X-ray neutron scattering studies reported nonzero moments long-range collinear order. While some experiments seem consistent with altermagnetism, remains controversial. We show that nonmagnetic, bulk thin film. Muon...
We observe a giant spin-orbit splitting in bulk and surface states of the non-centrosymmetric semiconductor BiTeI. show that Fermi level can be placed valence or conduction band by controlling termination. In both cases it intersects spin-polarized bands, corresponding depletion accumulation layers. The momentum these bands is not affected adsorbate-induced changes potential. These findings demonstrate two properties crucial for enabling semiconductor-based spin electronics -- large, robust...
Combinations of non-trivial band topology and long-range magnetic order hold promise for realizations novel spintronic phenomena, such as the quantum anomalous Hall effect topological magnetoelectric effect. Following theoretical advances material candidates are emerging. Yet, a compound with band-inverted electronic structure an intrinsic net magnetization remains unrealized. MnBi$_2$Te$_4$ is candidate first antiferromagnetic insulator progenitor modular (Bi$_2$Te$_3$)$_n$(MnBi$_2$Te$_4$)...
Spatial light modulators (SLMs) based on liquid crystals are widely used for wavefront shaping. Their large number of pixels allows one to create complex wavefronts. The crosstalk between neighboring pixels, also known as fringing field effect, however, can lead strong deviations. realized may deviate significantly from the prediction idealized assumption that response across a pixel is uniform and independent its neighbors. Detailed numerical simulations SLM full 3D physical model...
Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of chiral crystal. We have studied by spin- angle-resolved photoelectron spectroscopy its unconventional electronic structure unique spin texture. identify Kramers-Weyl, composite, accordionlike Weyl fermions, so far only predicted theory, show that polarization parallel to wave vector along lines in k space connecting high-symmetry points. Our...
The future of water-derived hydrogen as the "sustainable energy source" straightaway bets on success sluggish oxygen-generating half-reaction. endeavor to emulate natural photosystem II for efficient water oxidation has been extended across spectrum organic and inorganic combinations. However, achievement so far restricted homogeneous catalysts rather than their pristine heterogeneous forms. poor structural understanding control over mechanistic pathway often impede overall development....
Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss, in order provide more degrees of freedom manipulating propagating light. Here, we report a new method for femtosecond laser writing optical-fiber-compatible glass waveguides, namely spherical phase-induced multicore (SPIM-WG), which addresses this challenging task three-dimensional on-chip light control. Fabricating heating regime...
Atomic monolayers on semiconductor surfaces represent an emerging class of functional quantum materials in the two-dimensional limit - ranging from superconductors and Mott insulators to ferroelectrics spin Hall insulators. Indenene, a triangular monolayer indium with gap ~ 120 meV is insulator whose micron-scale epitaxial growth SiC(0001) makes it technologically relevant. However, its suitability for room-temperature spintronics challenged by instability topological character air. It...
Abstract A paradigmatic case of multi-band Mott physics including spin-orbit and Hund’s coupling is realized in Ca 2 RuO 4 . Progress understanding the nature this insulating phase has been impeded by lack knowledge about low-energy electronic structure. Here we provide—using angle-resolved photoemission electron spectroscopy—the band structure paramagnetic show how it features several distinct energy scales. Comparison to a simple analysis atomic multiplets provides quantitative estimate J...
The Rashba effect is fundamental to the physics of two-dimensional electron systems and underlies a variety spintronic phenomena. It has been proposed that formation Rashba-type spin splittings originates microscopically from existence orbital angular momentum (OAM) in Bloch wave functions. Here, we present detailed experimental evidence for this OAM-based origin by angle-resolved photoemission (ARPES) two-photon experiments monolayer AgTe on Ag(111). Using quantitative low-energy...
We investigate the polaronic ground state of anatase ${\mathrm{TiO}}_{2}$ by bulk-sensitive resonant inelastic x-ray spectroscopy (RIXS) at Ti ${L}_{3}$ edge. find that formation polaron cloud involves a single 95 meV phonon along $c$ axis, in addition to 108 $ab$-plane mode previously identified photoemission. The coupling strength both modes is same within error bars, and it unaffected carrier density. These data establish RIXS as directional probe electron-phonon solids.
Photovoltaic conversion efficiency of CuInSe 2 solar cells is limited by low fill factor ( FF ) and open‐circuit‐voltage V OC values compared to Si or perovskite cells. Herein, small quantities Ag alloy improve its properties are used, such as enhanced grain growth, higher crystal quality, less detrimental defects, overcome the device limitations low‐bandgap absorbers. The impact on electronic bulk material buffer–absorber interface examined at different stoichiometric compositions. alloying...
In nodal-line semimetals linearly dispersing states form Dirac loops in the reciprocal space, with high degree of electron-hole symmetry and almost-vanishing density near Fermi level. The result is reduced electronic screening enhanced correlations between quasiparticles. Here we investigate structure ZrSiSe, by combining time- angle-resolved photoelectron spectroscopy ab initio functional theory (DFT) complemented an extended Hubbard model (DFT +U +V). We show that are on ultrashort...
Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions. Key to engineer the topologically non-trivial band ordering and sizable gaps is strong spin-orbit interaction. Following Kane Mele's original suggestion, one approach synthesize monolayers of heavy atoms with honeycomb coordination accommodated templates hexagonal symmetry. Yet, in majority cases, this recipe leads triangular lattices, typically hosting metals or trivial...
The approach of photoemission orbital tomography, i.e., the density reconstruction from planar molecular layers by using a formalism equivalent to Fourier transformation, is transferred free atoms. Absolute radial densities neon $1s$, $2s$, and $2p$ orbitals are reconstructed with central-field one-electron model, well-known atomic photoionization data. model parameters optimized Markov chain Monte Carlo method Bayesian inference which uncertainties for derived. presented opens path...
The quantum spin Hall insulator bismuthene, a two-third monolayer of bismuth on SiC(0001), is distinguished by helical metallic edge states that are protected groundbreaking 800 meV topological gap, making it ideal for room temperature applications. This massive gap inversion arises from unique synergy between flat honeycomb structure, strong orbit coupling, and an orbital filtering effect mediated the substrate. However, rapid oxidation bismuthene in air has severely hindered development...