A5088330779- Physics of Superconductivity and Magnetism
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Semiconductor materials and devices
- 2D Materials and Applications
- Perovskite Materials and Applications
- Ferroelectric and Piezoelectric Materials
- Magnetic properties of thin films
- Superconducting Materials and Applications
- Iron-based superconductors research
- Graphene research and applications
- Multiferroics and related materials
- Plasmonic and Surface Plasmon Research
- Magnetic Properties of Alloys
- Quantum Dots Synthesis And Properties
- Rare-earth and actinide compounds
- Copper-based nanomaterials and applications
- ZnO doping and properties
- Optical Coatings and Gratings
- High-pressure geophysics and materials
- Topological Materials and Phenomena
- Quantum Chromodynamics and Particle Interactions
- Photoreceptor and optogenetics research
- Photonic Crystals and Applications
European X-Ray Free-Electron Laser
2024-2025
Paul Scherrer Institute
2019-2024
Swiss Light Source
2021-2024
National University of Singapore
2013-2023
Universität Hamburg
2023
Nanocore (Brazil)
2016
Abstract Semiconductor compounds are widely used for photocatalytic hydrogen production applications, where photogenerated electron–hole pairs exploited to induce catalysis. Recently, powders of a metallic oxide (Sr 1− x NbO 3 , 0.03< <0.20) were reported show competitive efficiencies under visible light, which was attributed interband absorption. This discovery expanded the range materials available optimized performance as photocatalysts. Here we study epitaxial thin films SrNbO 3+ δ...
Abstract Plasmonics has attracted tremendous interests for its ability to confine light into subwavelength dimensions, creating novel devices with unprecedented functionalities. New plasmonic materials are actively being searched, especially those tunable plasmons and low loss in the visible–ultraviolet range. Such commonly occur metals, but many metals have high optical range, a main issue current research. Here, we discover an anomalous form of correlated Mott-like insulating oxide from Sr...
The rising demand for high-performance lithium-ion batteries, pivotal to electric transportation, hinges on key materials like the Ni-rich layered oxide LiNi
<title>Abstract</title> A fundamental understanding of the interplay between lattice structure, polarization and electrons is pivotal to optical control ferroelectrics. The interaction light matter enables remote wireless ferroelectric on picosecond timescale, while inducing strain, i.e., deformation. At equilibrium, proportional typically assumed be so also out equilibrium. Decoupling from strain would remove constraint sample design provide an effective knob manipulate by light. Here, upon...
We report significant changes of optical conductivity (${\ensuremath{\sigma}}_{1}$) in single-layer graphene induced by mild oxygen plasma exposure and explore the interplay between carrier doping, disorder, many-body interactions from their signatures absorption spectrum. The first distinctive effect is reduction excitonic binding energy that can be extracted renormalized saddle point resonance at 4.64 eV. Secondly, ${\ensuremath{\sigma}}_{1}$ nearly completely suppressed...
Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse fluctuations may enhance the inter-stripe Josephson coupling and thus promote Direct experimental studies of dynamics, however, remain difficult. From a strong-coupling perspective, are realized in form dynamic "kinks"-sideways shifting sections. Here, we show how modest uniaxial pressure tuning reorganizes directional kink alignment. Our starting point La1.88Sr0.12CuO4 where ordering results...
Abstract In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with commensuration of eight four lattice units, respectively. How this evolves across optimal doping remains controversial question. Here we present systematic resonant inelastic x-ray scattering study weak correlations in La 2− x Sr CuO 4 1.8− Eu 0.2 . Ultra high energy resolution experiments demonstrate the importance separation elastic processes. Long-range...
The mechanism responsible for the extraordinary interface conductivity of ${\mathrm{LaAlO}}_{3}$ on ${\mathrm{SrTiO}}_{3}$ and its insulator-metal transition remains controversial. Here, using density functional theory calculations, we establish a comprehensive coherent picture that interplay electronic reconstructions, lattice distortions, surface oxygen vacancies fully compensates polarization potential divergence in ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$, explaining naturally...
Interfaces of two dissimilar complex oxides exhibit exotic physical properties that are absent in their parent compounds.
We use resonant inelastic x-ray scattering (RIXS) at the Fe-L_{3} edge to study spin excitations of uniaxial-strained and unstrained FeSe_{1-x}S_{x} (0≤x≤0.21) samples. The measurements on samples reveal dispersive in all doping levels, which show only minor dependence energy dispersion, lifetime, intensity, indicating that high-energy are marginally affected by sulfur doping. RIXS spin-excitation anisotropy observed previously FeSe is also present range 0<x≤0.21 FeSe_{1-x}S_{x}. persists a...
Patterning of the two-dimensional electron gas formed at interface two band insulators such as LaAlO3/SrTiO3 is one key challenges in oxide electronics. The use energetic ion beam exposure for engineering conductivity has been investigated. We found that this method can be utilized to manipulate by carrier localization, arising from defects created exposure, eventually producing an insulating ground state. This process ion-beam-induced defect creation results structural changes SrTiO3...
Electron-electron (e-e) and electron-hole (e-h) interactions are often associated with many exotic phenomena in correlated electron systems. Here, we report an observation of anomalous excitons at 3.75, 4.67, 6.11 eV 4.2 K bulk ${\mathrm{SrTiO}}_{3}$. Fully supported by ab initio $GW$ Bethe-Salpeter equation calculations, these due to strong e-h e-e different characters: 4.67 resonant 3.75 is a bound Wannier-like exciton unexpectedly higher level delocalization. Measurements calculations on...
Perovskite compounds show promise for charge generation in solar cells because of their high density excitons when exposed to light. New experiments reveal the origin this behavior, which could point way more efficient optoelectronic devices.
Recently, an anomalous generation of multiple plasmons with large spectral weight transfer in the visible to ultraviolet range (energies below band gap) has been experimentally observed insulatinglike phase oxygen-rich strontium niobium oxides (${\mathrm{SrNbO}}_{3+\ensuremath{\delta}}$). Here, we investigate ground-state and dielectric properties ${\mathrm{SrNbO}}_{3+\ensuremath{\delta}}$ as a function $\ensuremath{\delta}$ by means extensive first-principle calculations. We find that...
Abstract Electronic correlations play important roles in driving exotic phenomena condensed matter physics. They determine low-energy properties through high-energy bands well-beyond optics. Great effort has been made to understand excitations such as excitons transition metal dichalcogenides (TMDCs), however their and interlayer correlation remain mysteries. Herewith, by measuring temperature- polarization-dependent complex dielectric loss functions of bulk molybdenum disulphide from...
We present evidence of a drastic renormalization the optical conductivity graphene on $\mathrm{SrTiO}{}_{3}$ resulting in almost full transparency ultraviolet region. These findings are attributed to resonant excitonic effects further supported by ab initio Bethe-Salpeter equation and density functional theory calculations. The $(\ensuremath{\pi},\ensuremath{\pi}*)$ orbitals Ti-$3d$ ${t}_{2g}$ strongly hybridized interactions electron-hole states residing those play dominant role...
Electrolyte gating is widely used to induce large carrier density modulation on solid surfaces explore various properties. Most of past works have attributed the charge electrostatic field effect. However, some recent reports argued that electrolyte effect in VO2, TiO2, and SrTiO3 originated from field-induced oxygen vacancy formation. This gives rise a controversy about mechanism, it therefore vital reveal relationship between role intrinsic properties materials. Here, we report entirely...
We report the electronic structures of Ta-doped anatase TiO${}_{2}$ thin films grown by pulsed laser deposition (PLD) with varying magnetization using a combination first-principles calculations and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The roles Ta doping Ti vacancies are clarified, observed room-temperature ferromagnetism is attributed to localized magnetic moments at vacancy sites ferromagnetically ordered electron charge carriers. O $K$-edge spectra exhibit...
The interactions between delocalized and localized charges play important roles in correlated electron systems. Here, using a combination of transport measurements, spectroscopic ellipsometry (SE), X-ray absorption spectroscopy (XAS) supported by theoretical calculations, we reveal the role interfacial their screening effects determining mobility (La0.3 Sr0.7 )(Al0.65 Ta0.35 )O3 /SrTiO3 (LSAT/SrTiO3 ) interfaces. When LSAT layer thickness reaches critical value 5 uc, insulating interface...
Titanium dioxide (TiO$_2$) has rich physical properties with potential implications in both fundamental physics and new applications. Up-to-date, the main focus of applied research is to tune its optical properties, which usually done via doping and/or nano-engineering. However, understanding role $d$-electrons materials possible functionalization $d$-electron are still major challenges. Herewith, within a combination an innovative experimental technique, high energy conductivity,...
Tunable plasmons in the infrared energy range are of critical importance designing novel plasmonic materials with fascinating uses various solid-state applications, such as plasmonics, transformation optics, and biochemical sensors. Perovskite oxides promising building-block for plasmon generation because they have wide tunable band gaps well possibility having low loss. Here, using a combination high-resolution spectroscopic ellipsometry, x-ray-absorption spectroscopy both at...
We report the optical and electronic properties of multilayer graphene films grown epitaxially on carbon face (C-face) 4H-SiC probed using spectroscopic ellipsometry (SE) angle-resolved photoemission spectroscopy (ARPES). The conductivity in energy range from 1.0 to 5.3 eV extracted SE reveals two important features: presence universal at near-infrared region asymmetric resonant excitons 4.5 eV. Furthermore, ARPES shows independent linear dispersion. These features resemble...
We report the first observation of coexistence a distinct midgap state and Mott in undoped their evolution electron hole-doped ambipolar ${\mathrm{Y}}_{0.38}{\mathrm{La}}_{0.62}({\mathrm{Ba}}_{0.82}{\mathrm{La}}_{0.18}{)}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ films using spectroscopic ellipsometry x-ray absorption spectroscopies at O $K$ Cu ${L}_{3,2}$ edges. Supported by theoretical calculations, is shown to originate from antiferromagnetic correlation. Surprisingly, while magnetic...
Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO3 and SrTiO3 (LaAlO3/SrTiO3), striking interfacial magnetisms have been observed in LaAlO3/SrTiO3 heterostructures. Interestingly, the strength of magnetic moment is found to be dependent on oxygen partial pressures during growth process. This raises important, fundamental question origin these remarkable orderings. Here, we report a direct evidence room-temperature stable magnetism heterostructure...