A5069111720- Quantum, superfluid, helium dynamics
- Graphene research and applications
- Advanced Chemical Physics Studies
- Topological Materials and Phenomena
- Quantum and electron transport phenomena
- Surface and Thin Film Phenomena
- Thermal properties of materials
- Atomic and Subatomic Physics Research
- nanoparticles nucleation surface interactions
- Physics of Superconductivity and Magnetism
- Advanced Thermodynamics and Statistical Mechanics
- Advanced NMR Techniques and Applications
- Nuclear Physics and Applications
- Nanopore and Nanochannel Transport Studies
- Climate change and permafrost
- Quantum many-body systems
- Chemical and Physical Properties of Materials
- Superconductivity in MgB2 and Alloys
- Cryospheric studies and observations
- Digital Holography and Microscopy
- Arctic and Antarctic ice dynamics
- Surface Chemistry and Catalysis
- Experimental and Theoretical Physics Studies
- Optical measurement and interference techniques
- Ion-surface interactions and analysis
University of Cambridge
2016-2024
Cavendish Hospital
2016-2022
Technion – Israel Institute of Technology
2011
Magnetic fields can separate two isomers of water that differ in the relative spin states their hydrogen atoms.
We have studied the topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$(111) by means of helium atom scattering. The average electron-phonon coupling $\ensuremath{\lambda}$ is determined adapting a recently developed quantum-theoretical derivation scattering probabilities to case degenerate semiconductors. Based on Debye-Waller attenuation elastic diffraction peaks ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$(111), measured at surface temperatures between 110 and...
This paper presents material properties particularly suited to be measured with helium scattering techniques. Below a specific science case example illustrating the measurement of electron–phonon coupling constant <italic>λ</italic> on topological insulator surface.
Highly corrugated, stepped surfaces present regular 1D arrays of binding sites, creating a complex, heterogeneous environment to water. Rather than decorating the hydrophilic step sites form chains, water on Cu(511) forms an extended 2D network that binds strongly steps but bridges across intervening hydrophobic Cu(100) terraces. The hydrogen-bonded contains pentamer, hexamer, and octomer rings leave third stable Cu unoccupied in order bind H down close dipole complete three hydrogen bonds...
Abstract The microscopic motion of water is a central question, but gaining experimental information about the interfacial dynamics in fields such as catalysis, biophysics and nanotribology challenging due to its ultrafast motion, complex interplay inter-molecular molecule-surface interactions. Here we present an computational study nanoscale-nanosecond at surface topological insulator (TI), Bi $${}_{2}$$ <mml:math...
Helium diffraction has the potential to reveal degree of proton order at an ice surface, and been used in past benchmark theoretical work. We demonstrate that previous calculations do not represent experiment a sufficient accuracy. By combining realistic helium-water with quantum using exact close-coupling methods we scattering is strongly energy dependent. Proton may be inferred best from selective adsorption resonances helium atom, which involve multiple scattering. use results discuss...
The alignment of ultra-high-vacuum sample transfer systems can be problematic when there is no direct line sight to assist the user. We present design a simple and cheap system which greatly simplifies devices. Our method based on adaptation commercial digital camera provides live views from within vacuum chamber. images are further processed using an image recognition processing code determines any misalignments reports them Installation has proven extremely useful in order align with...
Diffraction measurements following the growth of h-BN, reveal intermediate long-range ordered open network structures during formation. DFT calculations explain their nature, outlining new routes to control synthesis covalent 2D networks.
We present helium scattering measurements of a water ad-layer grown on O(2 × 1)/Ru(0001) surface. The adsorbed layer results in well ordered diffraction pattern with systematic extinctions spots due to glide line symmetries. data reflects well-defined surface structure that maintains proton order even at surprisingly high temperatures 140 K. we measure is consistent recently derived from STM performed 6 Comparison recent DFT calculation partial agreement, suggesting these calculations might...
We present a determination of quasiparticle-phonon interaction strengths at surfaces through measurements phonon spectra with ultrahigh energy resolution. The lifetimes low surface phonons on pristine Ru(0001) were determined over wide range temperatures and an analysis the temperature dependence enables us to attribute separate contributions from electron-phonon interactions, phonon-phonon defect-phonon interactions. Strong interactions are evident all we show they dominate below 400 K.
The jump distribution, a property of the motion adsorbates on corrugated surface, contains crucial information adsorbate-substrate energy dissipation processes. To provide means to study distributions in honeycomb array adsorption sites, we derive analytical expressions for intermediate scattering function (ISF) describing diffusion taking into account jumps up fourth-nearest neighbor length. enable testing against experimental or simulated data, develop global fitting routine that can be...
A combined study of density functional theory calculations and<sup>3</sup>He spin echo spectroscopy, finds sodium to change adsorption site on Ru(0001), from hollow top, as the coverage is reduced.
Nanoscopic clustering in a 2D disordered phase is observed for oxygen on Ru(0001) at low coverages and high temperatures. We study the coexistence of quasistatic clusters (with characteristic length $\ensuremath{\sim}9\text{ }\text{ }\AA{}$) highly mobile atomic which diffuses between energy-inequivalent, threefold hollow sites substrate. determine surprisingly activation energy diffusion $385\ifmmode\pm\else\textpm\fi{}20\text{ }\mathrm{meV}$. The minimum...
The use of helium diffraction patterns to study desorption processes is explored as a novel extension traditional methods based on specular reflection. sample, cyclooctatetraene, adsorbed Cu(111) provides rich but complex structure. modulation cyclooctatetraene by manifested convolution in the pattern, displaying an averaged super cell symmetry (73×73)R30°. adlayer expands during isothermal desorption, and change lattice constant direct measure coverage function time. We find energy 0.96 ±...
The scattering of gas from surfaces underpins technologies in fields such as permeation, heterogeneous catalysis and chemical vapour deposition. effect surface defects on the is key technologies, but still poorly understood. It known empirically that unordered result-in random-angle scattering, with thought to be classical. We here demonstrate transition quantum mechanical diffraction cosine-scattering, show bound-state resonances can greatly affect this transition. Further, we find randomly...
Helium atom scattering studies have the potential for making numerous breakthroughs in study of processes on surfaces. As this field remains active, there will frequently be new young researchers entering field. The transition from student to researcher is often met with difficulty, consequently wasting limited time available a PhD or masters level research. Addressing issue, we present an educational package emerging research students helium scattering. We hope that serves as sufficient...
The study explores machine learning methods for revealing chemical sensitivity in Helium spin-echo spectroscopy, order to obtain ultra-sensitive surface analytic technique. We model bi-species co-adsorbed systems and demonstrate that by using deep-learning neural-networks partial concentrations are obtainable. An example system of particles with mass 50 100 a.m.u was tested characteristic inter-adsorbate adsorbate-substrate interactions, being resolvable up 20% occupancy adsorption sites,...
Large-area single-crystal monolayers of two-dimensional (2D) materials such as graphene and hexagonal boron nitride (h-BN) can be grown by chemical vapour deposition (CVD). However, the high temperatures fast timescales at which conversion from a gas-phase precursor to 2D material appear, make it extremely challenging simultaneously follow atomic arrangements. We utilise helium atom scattering discover control growth novel h-BN nanoporous phases during CVD process. find that prior formation...