Description
The Poster Session is held on Wed and Thu. All posters are to be presented on both days. However, due to technical reasons, the contributions are only listed in the timetable of Wed.
Black phosphorus (BP) consists of a layered puckered structure of P atoms in a hexagonal arrangement, with outstanding optical, [1] electrical [2] and thermal properties [3].
Unlike his carbon counterpart graphene, it exhibits a thickness-dependent electronic band gap, spanning from 2 eV for phosphorene (single layer) down to 0.33 eV for bulk BP.
Our trARPES experiment now shows that the...
A bottom-up approach allows for the synthesis of ultra-narrow graphene nanoribbons (GNR) with a sizeable bandgap and thus excellent candidates for switching applications. In this work we focused on 5- and 9-atom wide armchair GNRs (5-AGNR, 9-AGNR) grown under UHV conditions on Au(111) and Au(788) surfaces. GNRs were transferred using two different transfer approaches and for both 5- and...
InteractiveXRDFit is a Matlab program that calculates the X-ray diffracted intensity for heterostructures. Other fitting programs are already available and efficient, but may lack some flexibility with some of the parameters that this program allows modifying. Here the user can choose the substrate and the different materials composing an heterostructure among a long list of compounds (mainly...
$CsPbBr_3$ is a robust fully-inorganic semiconductor of the lead-halide family of perovskites (LHPs), whose outstanding properties and low cost promise several applications in photovoltaics, photodetectors, and optoelectronics. However, their band structure, which is fundamental to describe their interaction with light, remains poorly studied. By applying angle-resolved photoemission...
One-dimensional (1D) materials are important model systems. We present a high energy resolution ARPES study of NbSe$_{\mathrm{3}}$, a quasi-1D bulk material exhibiting three-dimensional charge density wave (CDW) phases at low temperature. Synchrotron measurements reveal CDW gaps in the electronic structure at energies well below the Fermi level ($E_{\mathrm{F}}$) [1], while ultra-high energy...
Here, we have studied the magnetically ordered phase of Ca$_{2}$RuO$_4$ at T = 16 K, using Oxygen K edge Resonant Inelastic X-ray Scattering (RIXS) technique. Four excitations have been identified – two low energy excitations labelled A and B at 80 meV and 400 meV respectively and two high energy excitations labelled C and D at 1.3 eV and 2.2 eV respectively. The A and B branches are...
Charge-carrier cooling in transition metal oxides is of outmost importance in photovoltaics where it affects the cell performances. In this study, charge-carrier cooling is investigated by femtosecond broadband UV spectroscopy with different pump wavelengths where the cooling can be monitored via a red-shifting optical bleach towards the optical gap energy. Lifetime density analysis provides...
Since the discovery of high temperature superconductivity in the
cuprates, this class of materials has been heavily investigated. However,
even after 30 years of research, the mechanisms that lead to their unique
behaviours are still not fully understood. Much focus has been given to their
electronic structure. Since these materials exhibit strong electron
correlations,...
Materials with antiferromagnetic interactions between spins on a triangle lattice inherently exhibit large frustration between similar energy ground states giving rise to new behavior. The kagomé lattice is an enticing example; however, various effects hinder its highly degenerate spin-liquid state and instead select a single magnetic ground state. It is therefore worthwhile to study...
Multiferroic materials are good candidates to realize ultrafast control of the magnetic and electric polarization simultaneously. This condition is met in $CoCr_2O_4$ (CCO), showing multiferroic properties below $T_s=27K$. This investigation concentrates on the effects of Ge-doping on ultrafast demagnetization dynamics below and above the multiferroic phase transition.
Femtosecond LASER pump,...
Ca$_{3}$Co$_{2}$O$_{6}$ is a frustrated Ising-like magnet with uniaxial anisotropy along its crystallographic c-axis. Magnetic field applied along this axis induces metamagnetic transition with occurrence of a magnetization plateau at ⅓ of maximum magnetization. We aim to understand the dynamics of this transition using bulk and microscopic methods and eliminate compound specific features to...
We performed deep-UV transient absorption spectroscopy of anatase-TiO2 sensitized by gold nanoparticles (NP). The advantage of the deep-UV is that the probe is sensitive to the excitonic transitions of TiO2. We detect electron injection upon excitation of both the interband transitions and the plasmon band of the NPs on time scales of 300 fs and < 500 fs (limitation of the time resolution),...
The bottom-up fabrication approach allows the growth of atomically precise graphene nanoribbons (GNRs). The fascinating properties, which originate from the unique electronic structure of GNRs, motivate wide interest in its potential application. In this work we synthesized 9-atom wide armchair GNRs under UHV conditions on a Au(11 12 12) crystal, allowing the growth of aligned GNRs. GNRs were...
Low-dimensional quantum magnets are of great fundamental importance due to strong quantum fluctuations which can produce novel quantum excitations and ground states. The 2D quantum (S = 1/2) Heisenberg antiferromagnet on a square lattice (2DQHAFSL) is one of the canonical interacting quantum systems. The chiral quantum magnet family A(bO)CU4(PO4)4...
In beam transport systems of a proton therapy machine, it is important to have an on-line measurement of the proton-beam intensity (nA). A non-interceptive beam intensity monitor has been developed for low-intensity beams for proton therapy machines without the hindrance of interceptive monitors. It works on the principle of a reentrant cavity resonator, matching its resonance frequency of...
An emerging new area in accelerator technologies is THz-driven devices. Optical rectification of infrared pulses gives intense phase-stable sources thus provides intrinsic synchronization without timing drifts and great temporal resolution. Generated single-cycle fields in the tens of MV/m range would allow downscaling of accelerator and beam diagnostic infrastructure.
Manipulation and...
We present here a method that allows data transfer through fog and clouds, based on the opto-mechanical displacement of the water droplets instead of directly interacting with them. We experimentally demonstrated this method, which is based on the use of two lasers and the detection of a 1 GHz amplitude modulated sinusoidal signal. A high peak power pulsed laser generates the cloudless channel...
In ice-covered enclosed water basins, the primary source of energy is the fraction of solar radiation that penetrates across the ice and reaches waters usually found below the temperature of maximum density. The radiative buoyancy flux works directly into the bulk, forcing increments of temperature/density in the upper fluid volume, which can become gravitationally unstable and drive...
This paper explores the potential of an atmospheric single-column model to analyse the nonlinear effects of a subgrid-scale mid-latitude open freshwater body. The are to propose a coupling technique between a combined land-open water surface and the atmosphere, to evaluate the nonlinear effects as the fractional areas of both surfaces increases incrementally from land to open water, and to...
Heat exhaust is one of the major issues in fusion research. The TCV tokamak has a large flexibility in the magnetic geometry of the plasma, allowing alternative divertor configuration studies in order to mitigate the tremendous heat and particle fluxes on the plasma-facing components. The envisioned divertor upgrade of TCV will introduce baffles to the divertor, which were predicted to...
Understanding the plasma dynamics in the scrape-off layer (SOL) is of fundamental importance on the way to fusion energy. For example, the SOL sets the boundary conditions for the tokamak core and it regulates the energy flux to the tokamak wall. With the goal of improving our understanding of the SOL, the GBS code was developed during the past years. GBS simulates the SOL turbulence by...
Proper understanding of turbulent transport is crucial to achieve controlled fusion. Numerically, turbulence can be studied in the gyrokinetic framework, where turbulent fluctuations are separated from the rapid gyration motion of the charged particles. Comparison with experimental observables can then be made through the application of a synthetic diagnostic. In this work we make use of a...
Exposure is a short-science-film hackathon for scientists and artists. Last held in Lausanne in November 2017, it united forty young science enthusiasts to learn and develop science communication skills by producing 3-minute short science films in just 3 days. We present here the “Sun in a Box” short-film which won the joint-best film voted by an expert jury. It attempts to beautifully share...
The n2EDM experiment being mounted at the Paul Scherrer Institute (PSI) will search for the neutron electric dipole moment (nEDM) with at least an order of magnitude better sensitivity than its predecessor at PSI. With the increment in statistical sensitivity, controls of systematic effects must follow. This study targets to investigate the impact of Johnson-Nyquist noise originating from...
Understanding the precise rigidity dependence of the Silicon flux sheds light on the origin, acceleration and propagation of cosmic rays. The Alpha Magnetic Spectrometer (AMS-02) provides measurements of cosmic rays with high accuracy. Data analysis procedures, focusing on charge selection and tracking efficiency calculation, will be presented.
The Beryllium isotopic composition in cosmic rays provides essential information for the study of the propagation of cosmic rays in the Galaxy. The Alpha Magnetic Spectrometer (AMS) installed on the International Space Station (ISS) provides the opportunity to measure this composition in the energy range from ~1 GeV/n to ~10 GeV/n with unprecedented precision. For events selected with a...
Measurements of decaying charge to decayed charge ratios in cosmic rays, such as Aluminum to Magnesium, allow to constrain the cosmic-ray residence time in the Galaxy, providing complementary information on cosmic-ray propagation with respect to what can be extracted from the Beryllium isotopic composition. With 115 billion cosmic-ray events collected by AMS-02 on the International Space...
The LHC will be upgraded to achieve higher instantaneous luminosity. The upgraded machine will be called HL-LHC with the next phase of data taking referred to as Phase II. A novel Monolithic Active Pixel Sensor (MAPS), dubbed MALTA, has been designed and is under investigation to assess its suitability for operation in the outer layers of the Phase II ATLAS pixel detector. A readout system has...
The motivation for the use of Mott scattered positrons will be shown: By correctly tuning the positron beam, the scattered positrons have similar properties as the expected signal. Thus, they are suitable candidates to fake a signal event in the MEGII Spectrometer to fully characterise the detector response and to extract the positron’s probability density functions used for the search of a...
The n2EDM experiment, presently under construction at PSI, aims at searching for the neutron electric dipole moment $d_n$, with at least an order of magnitude higher sensitivity than previous efforts. The systematic uncertainties must be better controlled than in the predecessor experiment. Due to different motional magnetic fields seen by the neutrons and Hg atoms of the co-magnetometer, a...
The family of decays mediated by $b \to s \ell^+ \ell^-$ transitions ($\ell = \mu, e$) provides a rich laboratory to search for effects of physics beyond the Standard Model. In recent years, LHCb has found hints of deviations from theoretical predictions in branching fraction ratios (\textit{i.e.} $R_{K}$ and $R_{K^{*0}}$) and angular distributions of the muonic channel. More recently,...
The early neutron electric dipole moment (EDM) experiments were performed using continuous beams. They were replaced in the 1980’s with ultracold neutron storage experiments as they provide better sensitivity due to longer observation times. A new approach, the BeamEDM experiment, is based on the early neutron EDM measurements, however, using a pulse beam. This allows to combine a...
Muonic hydrogen (mup) is a bound-state of a negative muon and a proton. Since a muon is 207 times heavier than an electron the energy levels of muonic hydrogen are very sensitive to the nuclear structure. By means of laser spectroscopy, we are aiming at the measurement of the ground-state hyperfine splitting (HFS) to extract the two-photon exchange contribution and the Zemach radius of the...
As a prequel for the novel pulsed neutron beam electric dipole moment (EDM) experiment, we have designed a smaller scale proof-of-principle experimental apparatus. The experiment represents a novel method to search for a CP-violating neutron EDM which is complementary to the current standard using ultracold neutrons. The setup consists of a set of aluminum cubes on which a neutron beam Ramsey...
After having observed the first diffuse astrophysical neutrino flux, IceCube has entered a new fascinating phase as it recently saw the first evidence of a point source responsible for a neutrino emission.
It is now crucial to set in place analyses that are able to search for time correlation between flaring objects emitting gamma-rays such as AGNs and neutrino emission and that could be run...
The TT-PET project aims at constructing a thin PET scanner with time-of-flight information for concurrent PET-NMR diagnostics. As part of the project a fully monolithic Si-Ge pixel sensor is currently being developed to meet the ambitious goal of a 30ps timing resolution for low energy photons. Lab characterization results of the analogue and digital front-end electronics for a prototype...
Currently the n2EDM experiment is under construction at PSI. Its purpose is to measure the neutron electric dipole moment (nEDM) with an order of magnitude better sensitivity than the predecessor experiment. As the experiment is sensitive to magnetic field changes it is important to be able to control the magnetic field in the magnetically challenging environment. A magnetic field mapping...
The study reports on an alternative method to generate transverse Landau damping to suppress coherent instabilities in circular accelerators. The idea is to produce the incoherent tune spread through detuning with longitudinal rather than transverse action. This approach is motivated by the high-brightness, low transverse emittance beams in future colliders where detuning with transverse...
LAr TPCs have been identified as one of the most promising technologies in neutrino physics, due to their excellent performance as high precision calorimeters and their ability to reconstruct in 3D the tracks of ionising particles. Future giant LAr TPCs, at the ten-kilotonne level, are now in the design and prototyping stage in the context of the Deep Underground Neutrino Experiment (DUNE)....
The High Energy cosmic-Radiation Detection (HERD) facility onboard China’s Space Station is planned for operation starting around 2025 for about 10 years. The application of the scintillating fiber tracker with silicon photomultiplier(SiPM) read-out as HERD tracker subsystem is proposed by the UniGE group. Different fiber tracker modules were developed and tested with the CERN SPS beam. An...
Rare semileptonic $b\to s\ell^+\ell^-$ transitions provide some of the most promising framework to search for new physics effects. Recent analyses of these decays have indicated an anomalous behaviour in measurements of angular distributions of the decay $B^0\to K^*\mu^+\mu^-$ and lepton-flavour-universality observables. Unambiguously establishing if these deviations have a common nature is of...
In recent years, it has become possible to investigate transport phenomena using ultracold atoms in a two-terminal configuration where two reservoirs are connected through a mesoscopic channel. The measurements, however, rely on comparing different samples because of the destructive nature of probing methods, which makes the measurements sensitive to even very weak fluctuation in the atomic...
The application of quantum-logic techniques to the spectroscopy of trapped atomic ions has enabled the determination of atomic properties at unprecedented levels of precision. Molecules have been proposed as suitable candidates for testing possible time-variation of fundamental constants, e.g. $\frac{m_p}{m_e}$ - ratio, and as long-coherence-time qubits. Our efforts focus on N$_2^+$ which has...
We investigate the mechanism of hole diffusion across leaky amorphous TiO$_2$ (am-TiO$_2$) layers. Through $\textit{ab initio}$ molecular dynamics simulations, we construct an atomistic model of am-TiO$_2$ consistent with the experimental characterization. We first demonstrate oxygen vacancies impossibly occur in am-TiO$_2$, which can be assimilated by the amorphous structure upon structural...
The Density Overlap Region Indicator (DORI) is a density-based scalar field, which reveals covalent bonding patterns and non-covalent interactions simultaneously. The present work goes beyond the traditional static quantum chemistry use of scalar fields and illustrates the suitability of DORI for analyzing geometrical and electronic signatures in highly fluxional systems. We show how DORI can...
Despite the success of linear-response time-dependent density functional theory (LR-TDDFT) in describing the photophysics of many molecular systems, its applicability has been limited by several substantial drawbacks, such as the description of charge-transfer and doubly excited states. Moreover, the approximate TDDFT functionals are unable to describe London dispersion interactions. Here, we...
Electrocatalysis is expected to play a key role in the development of a clean energy cycle. Understanding the reaction mechanism of target electrochemical processes is highly desirable in order to facilitate the design of novel catalyst materials. We present how first-principles calculations combined with an accurate implicit solvation model can contribute to shed light on the reaction...
The phonon Boltzmann equation developed by Peierls describes the heat conduction in solids in terms of the dynamics of interacting phonon wave-packets. This picture holds true only in a perfectly pure and infinite crystal. Several methods have been recently developed to solve this equation in a numerically exact way, allowing to determine the thermal conductivity of crystals.
Introducing...
Despite its simplicity the interacting homogeneous electron gas (HEG) is a paradigmatic test case in the study of the electronic structure of condensed matter. Beside being a model for valence electrons in simple metals, it also provides the basic ingredient for key electronic-structure theories. Here we propose to study it with many-body perturbation theory (MBPT), including diagrams beyond...
Koopmans-compliant functionals provide a novel orbital-density-dependent framework for an accurate evaluation of spectral properties by imposing a generalized piecewise-linearity condition on the total energy of the system with respect to the occupation of each orbital. Because of the orbital-density-dependent nature of the functionals, minimization of the total energy leads to a ground-state...
We present time- and angle-resolved photoemission spectroscopy (TR-ARPES) measurements on BixSb(2−x)TeySe(3−y) topological insulators. Exploiting circularly polarized femtosecond pulses we investigated spin-related ultrafast phenomena as photo-induced spin current and spin-dependent relaxation processes.
In particular, we report the first experimental evidence of a direct coupling between...
Topological insulators have emerged as a novel quantum state of matter[1,2]. The Dirac-like surface state and the peculiar spin-texture play an essential role in manipulating spin-polarization and spin-current. For future topological-based devices, a fine tailoring of electronic properties and robustness against air exposure are required. An innovative approach may rely on lead-based ternary...
Designed band engineering via perturbative superlattice potentials, inspired by graphene on hexagonal boron nitride substrate, potentially allows to induce topological bands. Making use of the general form of a substrate potential as dictated by symmetry, we derive the low-energy mini-bands of an hexagonal superstructure. Assuming a large supercell, we focus on a single Dirac cone (or valley)...
Topological insulators are commonly described using dimensional reduction from higher dimensional systems, e.g., charge transport in 1-dimensional Thouless pumps is mapped by dimensional reduction to the 2-D quantum Hall effect. Recently, a class of 2-dimesnional lattices has emerged where localized modes exist not only on the edges (1D) but also on the corners (0D). In this talk, I will...
Entanglement properties are routinely used to characterize phases of quantum matter in theoretical computations. For example the spectrum of the reduced density matrix, or so-called "entanglement spectrum", has become a widely used diagnostic for universal topological properties of quantum phases. However, while being convenient to calculate theoretically, it is notoriously hard to measure in...
SwissFEL is PSI’s new FEL facility. It is a 740 m long accelerator which goal is to provide 6-30 fs long pulses of light with wavelength of 1-70 Å at 100 Hz [1, 2]. In order to support flexible beam rates, machine protection assistance and flexible event rates, a reliable and flexible event timing system is required, which is capable to provide event distribution at 142.8 MHz and flexible...
Artificially designed arrays of nanostructures with a microstructure at sub-micrometer length scales can exhibit unique functionality, especially when built from a combination of different classes of materials. We present an overview of a novel magneto-mechanical material, where the coupling between nanoscale magnets embedded in a soft polymer matrix is exploited to control its mechanical...
The anomalous Nernst effect in a perpendicularly magnetized Ir$_{22}$Mn$_{78}$/Co$_{20}$Fe$_{60}$B$_{20}$/MgO thin film is measured using well defined in-plane temperature gradients. The anomalous Nernst coefficient reaches 1.8 $\mu$V/K at room temperature, which is almost 50 times larger than that of a Ta/Co$_{20}$Fe$_{60}$B$_{20}$/MgO thin film with perpendicular magnetic anisotropy. The...
Quasicrystals exhibit long range order but an absence of translational invariance, and therefore, quasicrystals possess non-identical local environment. In our studies we fabricated artificial ferromagnetic quasicrystals (AFQs) made of 19 nm thick CoFeB film with nanoholes in an arrangement of Penrose tiling, and investigated collective spin excitations by means of broadband spin-wave...
A parametric excitation is an effective way to excite short waved spin waves. We demonstrate an all electrical approach to measure the parametrically excited spin waves in yttrium iron garnet (YIG) films in that we exploited the frequency offset mode of vector network analyzer. The magnon spectra show a very narrow linewidth for the YIG LPE films close to the reported linewidth due to the...
Magnonic crystals are interesting for spin-wave based data processing. We investigate one-dimensional magnonic crystals (1D MCs) consisting of bistable CoFeB nanostripes separated by 75 nm wide air gaps. By adjusting the magnetic history, we program a single stripe of opposed magnetization in an otherwise saturated 1D MC. Its influence on propagating spin waves is studied via broadband...
Extending magnetic structures to the third dimension can lead to new properties such as magnetochi-rality effects and high data storage densities [1]. For the fabrication of three-dimensional magnetic nanostructures, suitable deposition methods need to be developed, as techniques such as sputtering lead to significant shadowing effects [2]. Here, we present the electroless deposition of NiFe...
Anomalous magnetic properties in 3d transition metal nanoparticles are often observed, but are still poorly understood. Here, we combine X-ray photo-emission electron microscopy with high-angle annular dark-field scanning transmission electron microscopy in order to correlate magnetism and microstructure of individual nanoparticles. The data are compared to simulated STEM images and atomistic...
Spin waves (magnons) are collective spin excitations in magnetically ordered materials. If exhibiting sub-100 nm wavelength they could become the information carrier of future non charge-based information technology. Due to wavelength mismatch interfacing magnons with microwaves is however challenging. We investigate ferrimagnetic nanoparticles as possible magnon nanoemitters. For this we...
Ferromagnetic nanotubes are promising candidates for high density magnetic storage technology,due to the possibility to define flux-closure remnant states and control their magnetization reversal processes via geometrical parameters such as length,inner and outer diameter.They form interesting nanoelements also in the field of magnonics, allowing for tailored shape-induced spin wave...
Skyrmions are of potential interest for future memory and memristive devices, opening new possibilities for nanoscale magnetism. Neel skyrmions or hedge-hog skyrmions were reported in systems with perpendicular magnetic anisotropy. Here we report the presence of out-of-plane magnetization spin structures (probably Neel skyrmion) in a single layer of Ta/Co/Pt with in-plane anisotropy using...
Two-dimensional XY spin systems have interesting thermodynamic phase diagrams that so far have been mainly explored theoretically. Thermally-active artificial spin systems provide the opportunity to study the phase transitions and thermal behaviour of experimentally difficult to realize two-dimensional spin systems. Here, we experimentally investigate the artificial XY system of...
Magnonic crystals (MCs), a metamaterial with artificially introduced periodicity, offer many possibilities to control spin wave propagation within them [1]. Spin waves propagating in opposite directions can have different amplitudes or frequencies, which is known as spin wave nonreciprocity [2]. The aim of this work is to enhance spin wave nonreciprocity in bi-component MCs based on...
Magnetic skyrmions are topologically non-trivial spin textures, which hold big promise for their use in potential spintronic devices. We have performed real time and real space investigations on skyrmion lattices (SkL) in Cu2OSeO3 using Lorentz microscopy to study magnetic field induced melting of the SkL and its heat-induced rotation. We particularly highlight the methods we use for the...
We want to look for a spin-dependence in the charge transfer that occurs at the interface between an electrode and an electrolyte. We are using p-GaAs and GaN/AlGaN functionalized with chiral molecules as working electrodes in a methyl-viologen solution. To avoid magneto-hydrodynamic effects, we use electrically detected electron paramagnetic resonance (ED-EPR) to detect a spin effect without...
Current-induced spin-orbit torque switching of perpendicular magnetization requires the application of an external magnetic field collinear with the current to ensure deterministic reversal. Recently, a number of approaches have been proposed to control the magnetization in absence of the field, for example by employing antiferromagnets or introducing lateral structural asymmetries. Here,...
Traction forces are critical for the interaction of the cell with its environment, cell polarization and motion. We have recently observed that traction stress that the cell exerts on the substrate is correlated to the cell-edge dynamics and increases with the distance between the cell edge and the center. In this work, we test if these features of traction force distribution could be...
An infection with a pathogen is especially dangerous in cases of developed resistance to currently available drugs. Depending on the infecting agent, the onset of disease may progress quickly. Culture-based conventional susceptibility assays take days and weeks to complete, in order to chose the right drug and dose. Our work considers the nanomechanical sensor that responds to miniscule...
Nowadays, sharpened glass fiber – made probes attached to a quartz tuning fork (TF) and exploiting the shear force – based feedback are by far the most popular in the field of SNOM. These probes are expensive, very fragile and their fabrication is difficult, hard to control and in many cases a hazardous process. Here we are presenting the first SNOM probes made from different plastic optical...
With the misuse of antibiotics and the increasing number of multi-resistant
living organisms, antimicrobial resistance becomes a very serious public
health issue. Conventional techniques for antibiotic sensitivity
characterization requires 24 h to one month.
Our group developed a cantilever based nanomotion detector that provides the same result in less than one hour. The organism of interest...
MRI is a versatile and widely used imaging technique, which is based on the principles of NMR. However, both techniques suffer from an inherent insensitivity due to very small levels of polarization. By combining hyperpolarization techniques with detection of the NMR signal through the asymmetry of radioactive beta or gamma decay an increase in NMR sensitivity by almost 10 orders of magnitude...
