Martin Wolf
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View article: THz‐Driven Coherent Phonon Fingerprints of Hidden Symmetry Breaking in 2D Layered Hybrid Perovskites
THz‐Driven Coherent Phonon Fingerprints of Hidden Symmetry Breaking in 2D Layered Hybrid Perovskites Open
Metal‐halide perovskites (MHPs) emerged as a family of novel semiconductors with outstanding optoelectronic properties for applications in photovoltaics and light emission. Recently, they also attract interest as promising candidates for s…
View article: Submolecular‐Resolution Probing of Vibrational Anharmonicity Using Tip‐Enhanced Raman Spectroscopy
Submolecular‐Resolution Probing of Vibrational Anharmonicity Using Tip‐Enhanced Raman Spectroscopy Open
Vibrational spectroscopy can reach atomic spatial resolution via highly confined optical probes, offering local chemical insight. Yet, overtones and combination bands have not fully benefited due to weak transition moments. Here, we show s…
View article: Submolecular‐Resolution Probing of Vibrational Anharmonicity Using Tip‐Enhanced Raman Spectroscopy
Submolecular‐Resolution Probing of Vibrational Anharmonicity Using Tip‐Enhanced Raman Spectroscopy Open
Vibrational spectroscopy can reach atomic spatial resolution via highly confined optical probes, offering local chemical insight. Yet, overtones and combination bands have not fully benefited due to weak transition moments. Here, we show s…
View article: Ultraconfined terahertz phonon polaritons in hafnium dichalcogenides
Ultraconfined terahertz phonon polaritons in hafnium dichalcogenides Open
View article: Depth-Resolved Vibrational SFG/DFG Spectroscopy of the Anisotropic Water Structure at Charged Interfaces
Depth-Resolved Vibrational SFG/DFG Spectroscopy of the Anisotropic Water Structure at Charged Interfaces Open
The molecular structure of water at charged aqueous interfaces is shaped by interfacial electric fields, which can induce significant anisotropy in the molecular orientations that extends over nanometer-scale distances. Despite great relev…
View article: Orbital mixing as key ingredient for magnetic order in a van der Waals ferromagnet
Orbital mixing as key ingredient for magnetic order in a van der Waals ferromagnet Open
Recent years have seen a vast increase in research onto van der Waals magnetic materials, due to the richness of many-body effects and the versatility for next-generation technologies. In many of these systems, magnetism is introduced via …
View article: Scattering near-field optical microscopy at 1-nm resolution using ultralow tip oscillation amplitudes
Scattering near-field optical microscopy at 1-nm resolution using ultralow tip oscillation amplitudes Open
Scattering-type scanning near-field optical microscopy (s-SNOM) allows for the observation of the optical response of material surfaces with a resolution far below the diffraction limit. Based on amplitude-modulation atomic force microscop…
View article: Atomic-scale ultrafast dynamics of local charge order in a THz-induced metastable state of 1T-TaS2
Atomic-scale ultrafast dynamics of local charge order in a THz-induced metastable state of 1T-TaS2 Open
Light-induced control of quantum materials enables manipulation of electronic and structural phases on ultrafast timescales. Probing their atomic-scale dynamics is essential to understand the role of defects and domain boundaries, but conv…
View article: Picocavity-Enhanced Raman Spectroscopy of Physisorbed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">D</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> Molecules
Picocavity-Enhanced Raman Spectroscopy of Physisorbed and Molecules Open
We report on tip-enhanced Raman spectroscopy of H2 and D2 molecules physisorbed within a plasmonic picocavity at 10 K. The intense Raman peaks resulting from the rotational and vibrational transitions are observed at subnanometer gap dista…
View article: Full Crystallographic Imaging of Hexagonal Boron Nitride Monolayers with Phonon-Enhanced Sum-Frequency Microscopy
Full Crystallographic Imaging of Hexagonal Boron Nitride Monolayers with Phonon-Enhanced Sum-Frequency Microscopy Open
Hexagonal boron nitride (hBN) is an important 2D material for van der Waals heterostructures, single photon emitters, and infrared nanophotonics. The optical characterization of mono- and few-layer samples of hBN however remains a challeng…
View article: Distortion-free sampling of ultrabroadband terahertz electric fields by interfacial spin accumulation
Distortion-free sampling of ultrabroadband terahertz electric fields by interfacial spin accumulation Open
In spintronics, FM|HM stacks consisting of a ferromagnetic-metal (FM) and a heavy-metal (HM) layer are model systems for spin transport and spin-charge interconversion. To explore their potential as detectors for ultrabroadband terahertz e…
View article: THz-Driven Coherent Phonon Fingerprints of Hidden Symmetry Breaking in 2D Layered Hybrid Perovskites
THz-Driven Coherent Phonon Fingerprints of Hidden Symmetry Breaking in 2D Layered Hybrid Perovskites Open
Metal-halide perovskites (MHPs) emerged as a family of novel semiconductors with outstanding optoelectronic properties for applications in photovoltaics and light emission. Recently, they also attract interest as promising candidates for s…
View article: Electro-optic cavities for in-situ measurement of cavity fields
Electro-optic cavities for in-situ measurement of cavity fields Open
View article: Plasmonic Light Emission by Inelastic Charge Transport in Ultrathin Zinc Oxide/Metal Heterostructures
Plasmonic Light Emission by Inelastic Charge Transport in Ultrathin Zinc Oxide/Metal Heterostructures Open
Controlling light emission from plasmonic nanojunctions is crucial for developing tunable nanoscale light sources and integrated photonic applications. It requires precise engineering of plasmonic nanocavity electrodes and a detailed under…
View article: Surface Phonon Polariton Ellipsometry
Surface Phonon Polariton Ellipsometry Open
View article: Using phase-resolved vibrational sum-frequency imaging to probe the impact of head-group functionality on hierarchical domain structure in lipid membranes
Using phase-resolved vibrational sum-frequency imaging to probe the impact of head-group functionality on hierarchical domain structure in lipid membranes Open
State-of-the-art sum-frequency generation microscopy quantitatively reveals the heterogeneous changes in density, order, and composition from PS-lipid exposure in model membranes.
View article: Frontier orbitals control dynamical disorder in molecular semiconductors
Frontier orbitals control dynamical disorder in molecular semiconductors Open
Charge transport in organic semiconductors is limited by dynamical disorder. Design rules for new high-mobility materials have therefore focused on limiting its two foundations: structural fluctuations and the transfer integral gradient. H…
View article: Sum-Frequency Generation Spectroscopy of Aqueous Interfaces: The Role of Depth and Its Impact on Spectral Interpretation
Sum-Frequency Generation Spectroscopy of Aqueous Interfaces: The Role of Depth and Its Impact on Spectral Interpretation Open
View article: Picocavity-Enhanced Raman Spectroscopy of Physisorbed H$_2$ and D$_2$ Molecules
Picocavity-Enhanced Raman Spectroscopy of Physisorbed H$_2$ and D$_2$ Molecules Open
We report on tip-enhanced Raman spectroscopy of H2 and D2 molecules physisorbed within a plasmonic picocavity at 10 K. The intense Raman peaks resulting from the rotational and vibrational transitions are observed at subnanometer gap dista…
View article: Scattering near-field optical microscopy at 1-nm resolution using ultralow tip oscillation amplitudes
Scattering near-field optical microscopy at 1-nm resolution using ultralow tip oscillation amplitudes Open
Scattering-type scanning near-field optical microscopy (s-SNOM) allows for the observation of the optical response of material surfaces with a resolution far below the diffraction limit. Based on amplitude-modulation atomic force microscop…
View article: Extracting the Heterogeneous 3D Structure of Molecular Films Using Higher Dimensional SFG Microscopy
Extracting the Heterogeneous 3D Structure of Molecular Films Using Higher Dimensional SFG Microscopy Open
Ultrathin molecular films are widespread in both natural and industrial settings, where details of the molecular structure such as density, out-of-plane tilt angles, and in-plane directionality determine their physicochemical properties. M…
View article: Unidirectional ray polaritons in twisted asymmetric stacks
Unidirectional ray polaritons in twisted asymmetric stacks Open
View article: Sum-frequency generation spectro-microscopy in the reststrahlen band of wurtzite-type aluminum nitride
Sum-frequency generation spectro-microscopy in the reststrahlen band of wurtzite-type aluminum nitride Open
Nonlinear-optical microscopy and spectroscopy provide detailed spatial and spectroscopic contrast, specifically sensitive to structural symmetry and order. Ferroics, in particular, have been widely studied using second harmonic generation …
View article: Ambitwistor Yang-Mills Theory Revisited
Ambitwistor Yang-Mills Theory Revisited Open
Inspired by the Movshev-Mason-Skinner Cauchy-Riemann (CR) ambitwistor approach, we provide a rigorous yet elementary construction of a twisted CR holomorphic Chern-Simons action on CR ambitwistor space for maximally supersymmetric Yang-Mil…
View article: How Thick is the Air–Water Interface?─A Direct Experimental Measurement of the Decay Length of the Interfacial Structural Anisotropy
How Thick is the Air–Water Interface?─A Direct Experimental Measurement of the Decay Length of the Interfacial Structural Anisotropy Open
The air-water interface is a highly prevalent phase boundary impacting many natural and artificial processes. The significance of this interface arises from the unique properties of water molecules within the interfacial region, with a cru…
View article: Rotating spintronic terahertz emitter optimized for microjoule pump-pulse energies and megahertz repetition rates
Rotating spintronic terahertz emitter optimized for microjoule pump-pulse energies and megahertz repetition rates Open
Spintronic terahertz emitters (STEs) are powerful sources of ultra-broadband single-cycle terahertz (THz) field transients. They work with any pump wavelength, and their polarity and polarization direction are easily adjustable. However, a…
View article: Atomic-precision control of plasmon-induced single-molecule switching in a metal–semiconductor nanojunction
Atomic-precision control of plasmon-induced single-molecule switching in a metal–semiconductor nanojunction Open
Atomic-scale control of photochemistry facilitates extreme miniaturisation of optoelectronic devices. Localised surface plasmons, which provide strong confinement and enhancement of electromagnetic fields at the nanoscale, secure a route t…
View article: Berry curvature signatures in chiroptical excitonic transitions
Berry curvature signatures in chiroptical excitonic transitions Open
The topology of the electronic band structure of solids can be described by its Berry curvature distribution across the Brillouin zone. We theoretically introduce and experimentally demonstrate a general methodology based on the measuremen…
View article: Sum-Frequency Generation Spectro-Microscopy in the Reststrahlen Band of Wurtzite-type Aluminum Nitride
Sum-Frequency Generation Spectro-Microscopy in the Reststrahlen Band of Wurtzite-type Aluminum Nitride Open
Nonlinear-optical microscopy and spectroscopy provide detailed spatial and spectroscopic contrast, specifically sensitive to structural symmetry and order. Ferroics, in particular, have been widely studied using second harmonic generation …
View article: Atomic wires on substrates: Physics between one and two dimensions
Atomic wires on substrates: Physics between one and two dimensions Open
Wires having a width of one or two atoms are the smallest possible physical objects that may exhibit one-dimensional properties. In order to be experimentally accessible at finite temperatures, such wires must stabilized by interactions in…