Description
The Poster Session is held on Tue and Wed. All posters are to be presented on both days. However, due to technical reasons, the contributions are only listed in the timetable of Tue.
We use far-infrared ellipsometry to determine the anisotropic optical response of the TbMnO3 film in the spectral range of 100-700 cm-1 and temperature range of 10-300 K. The 44 nm thick sample was grown by Pulsed Laser Deposition on an orthorhombic YAlO3 (010) substrate.
We were able to extract phonons properties, and observe softening due to the multiferroic phase transition. The analysis...
We will present a new magneto-ellipsometric instrument built at the Physics Department, University of Fribourg. It is based on combination of time-domain terahertz and Fourier-transform infrared spectrometers, equipped with He-flow cryostat and split-coil 7 Tesla magnet.
Apart from standard transmission geometry, the instrument is designed for reflection ellipsometry measurements at angles...
We report the pulsed laser deposition (PLD) of multilayers of the cuprate high-$\mathrm{T_C}$ superconductor $\mathrm{YBa_2Cu_3O_{7-\delta}}$ (YBCO) and the iridate $\mathrm{Sr_2IrO_4}$ (SIO) which exhibits a strong spin-orbit-coupling (SOC). The magneto-transport characteristics of the heterostructures are investigated.They reveal a strong and comparatively long-ranged proximity effect. This...
Resonant ultrasound (RUS) probes the resonant frequencies of a solid to determine the complete elastic tensor. RUS is sensitive to detect both the symmetry variation and coupling of other degrees of freedoms to the lattice. Notably, novel electronic ground states may be detected due to their symmetry breaking order parameters resulting in a change of resonant frequencies. Similarly, the...
In quantum magnets, simple degrees of freedom with short-range interactions lead to a plethora of emergent many-body phases with different exotic properties. Uniaxial pressure allows tuning these interactions selectively and engineer the underlying Hamiltonians. Hence, the properties of the emergent phases can be controlled on-demand.
One system where such selective tuning is very pertinent...
For the doped samples with a nominal compositions of K3-p-terphenyl, we observed a pronounced enhancement of some low-energy phonon modes that is in fair agreement with the prediction of lattice dynamical calculations. Moreover. We observed electronic excitations that give rise to a pronounced polaronic band and a weak Drude-like peak at the origin that is due to free carries with a plasma...
Layered transition metal dichalcogenides are an example of the van der Waals (vdW) materials, hosting many interesting states of matter like charge density wave ordering and superconductivity. In many vdW systems, the material properties can be profoundly and surprisingly sensitive to seemingly minor changes in composition or structure. Currently we are investigating vanadium intercalated...
A technique to unlock spatial resolutions in the order of 10$\,$nm is soft x-ray ptychography. Ptychography consists of moving the sample through a beam of monochromatic x-rays, all the while collecting diffraction patterns from the overlapping illumination spots. Recovery of the complex transmission function is achieved with a reconstruction algorithm. Measurements in the soft x-ray regime...
Superconducting circuits and spins confined in semiconductor structures represent two leading qubit implementations. Continuous fabrication improvements and a better understanding of semiconductor-oxide interfaces are crucial to enhancing qubit performance.
We use noise spectroscopy in silicon quantum dots to evaluate the substrates and oxides. Furthermore, we present a novel design for...
By means of the ultrafast electronic diffraction (UED) in reflection geometry, we observe argon atoms adsorbed of graphite with atomic resolution. The diffraction patterns of solid argon adsorbed on graphite compared with simulation shows FCC structure in (111) orientation.
Interesting physical phenomena emerge from the experiment as the phase diagram dependence on substrate surface ; the...
ZrSe2 in its pristine bulk form is an insulator and does not support a CDW phase. However, a recent study of mono- and few-layer ZrSe2 on graphene reports the observation of a 2x2 CDW driven by charge transfer from the substrate.[1]
We use cryogenic STM and STS to study in-situ cleaved bulk ZrSe2 and present a spatial spectroscopic investigation of native defects and their influence on the...
Silicon FinFETs are used in classical CMOS electronics but can also provide an attractive platform for the implementation of spin qubits. Classical transistors usually have highly doped contacts that determine device polarity (n-type or p-type). Our FinFET quantum dots have Schottky contacts formed by a silicide. These contacts can be ambipolar for a midgap silicide such as e.g. NiSi. For a...
Exotic states of matter are predicted to be found in 2D bilayer systems such as InAs/GaSb heterostructures. These are usually described as two adjacent quantum wells of InAs and GaSb where the conduction band of the former lies below the valence band of the latter. We present a variation of this structure using an insulating AlSb barrier between InAs and GaSb layers, acting as an n and a p...
Magnetohydrodynamics (MHD) is a powerful tool to assess the stability of laboratory plasmas. However, kinetic corrections to MHD can be crucial in the weakly collisional environment of a modern tokamak. The ultimate goal of this project is the implementation of a hybrid kinetic-MHD spectral code, which can capture kinetic effects while retaining the advantages and essential structure of the...
High-voltage AC power grids are commonly modeled as networks of coupled oscillators. Following a disturbance, the voltage frequencies exhibit coherent wave phenomena. These phenomena are well understood in networks with weakly connected areas. However, these oscillations have also been observed in well-connected large-scale grids. Understanding these phenomena is of great importance as...
The LEMING experiment aims to test the equivalence principle for second-generation matter, using a cold muonium beam (bound $\mu^+ e^-$), where the inertial mass is dominated by the muon.
The feasibility of such a measurement relies on measuring the gravitational deflection of a lifetime-limited atomic beam. In this poster, the feasibility of an atomic interferometer is discussed, which could...
SU(2) gauge theory with $N_f=24$ massless fermions is non-interacting at long distances, i.e. it has an infrared fixed point at vanishing coupling. With massive fermions the fermions are expected to decouple at energy scales below the fermion mass, and the infrared behavior is that of confining SU(2) pure gauge theory. We demonstrate this behavior non-perturbatively with lattice Monte Carlo...
A small, 18-cm bending radius double-focalizing spectrometer has been in use for the investigation of beta spectra from radioactive sources since its construction around 1995, equipped with a small solid-state detector and a state-of-the-art readout. Extensive datasets have been collected to calibrate the device and understand its behaviour, to be leveraged in the measurement of beta spectra...
Developing and understanding novel quantum materials pushes angle-resolved photoemission (ARPES) into new frontiers of resolution and extreme conditions. ULTRA endstation at the SIS beamline of the Swiss Light Source is a novel system for high-resolution ARPES at temperatures down to 4 K. With independent 6-axis control, minimal thermal drift, deflector scanning, and easy alignment, ULTRA is...
Soft-X-ray ARPES in photon-energy range around 1 keV combines electron-momentum resolution with large photoelectron escape depth, allowing studies of buried heterostructures and impurities. For example, experiments on AlGaN/GaN find anisotropy of the interfacial states, propagating to electron transport [Nature Comm. 9 (2018) 2653]. For LaAlO3/SrTiO3, resonant photoexcitation of Ti-derived...
The electron spin is the crucial parameter of modern spintronics and therefore its determination in energy structures of solids is highly important. In order to boost spin-resolved ARPES' efficiency and accessibility, a prototype of a new imaging-type multichannel spin detector for electrons based on Mott scattering is being developed. We present the current status of the project, focusing on...
Electron-boson interaction is quantified through the Eliashberg function $\alpha^2F(\omega,\mathbf{k})$, accessible through the electron self-energy $\Sigma(\varepsilon,\mathbf{k})$. In ARPES, $\Sigma(\varepsilon,\mathbf{k})$ is readily extracted from the spectral function, requiring little more than a parametric expression for the quasiparticle dispersion $\xi(\mathbf{k})$ in order to discern...
Probing the electronic properties of two-dimensional (2D) dopant layers ($\delta$-layers) in silicon is crucial to establish the quasi-2D characteristics of functional quantum-electronic devices. Here, we present the first soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) measurements of silicon $\delta$-layers. The SX regime allows us to directly probe through the native surface...
With an established model[1,2], we determine the attosecond photoemission time delay in the charge density wave material CuTe, by means of spin- and angle-resolved photoemission spectroscopy. While accessing absolute time delay information by measuring spin polarization as a function of binding energy, with its moderate correlation strength, this result constitutes a part of the study on the...
We present preliminary data measured in the multiferroic Y-type hexaferrite Ba1.3Sr0.7CoZnFe11AlO22 representing the time-resolved response of the crystal structure after short and intense THz excitation of an electromagnon. Electromagnons are emergent collective excitations that consist of optical phonons strongly coupled to magnons. It is believed that an electromagnon can alter the magnetic...
Quantum spin-liquids (QSLs) are novel phases of quantum matter defined by a highly-fluctuating and massively entangled ground state as T -> 0 K. A candidate QSL material is YbBr3, an effective spin-1/2 2D honeycomb system.
Inelastic neutron scattering experiments on this material reveal a broad continuum of scattering associated with strong quantum fluctuations of the magnetic system,...
Ce3TiSb5 belongs to the class of frustrated Kondo-lattice systems. We have carried out detailed magnetization and specific heat measurements that reveal a complex magnetic phase diagram. We also report our results from recent single crystal neutron diffraction to investigate the magnetic order. Most notably, we found reentrant magnetic order as a function of magnetic field.
Many neutron scattering experiments rely on single crystal mosaics, to optimize the overall scattering mass volume. Such alignment of mosaics is typically done through tedious and time-consuming manual labour. Here we present a semiautomated protocol for alignment of quasi-two-dimensional materials.
Kagome ice is a two dimensional critical state of algebraic spin correlations formed by applying a moderate magnetic field along the [111] direction of a pyrochlore spin ice. Field tilts away from perfect alignment tune the algebraic correlations, leading to symmetry-sustaining Kasteleyn transitions. We present a detailed experimental/theoretical study of the kagome ice Coulomb phase,...
I will present our current understanding of the magnetic degrees of freedom in Ni3TeO6, a non-centrosymmetric hexagonal material that undergoes a field-induced first-order phase transition with emergent multiferroic properties. Using neutron scattering under in-plane magnetic fields we find that the collinear spin structure becomes likely chiral at large fields. The low-energy spin-wave...
A correlated liquid state was reported in the cerium stannate pyrochlore Ce2Sn2O7 at temperatures below 1 Kelvin. Its nature remained elusive, but with additional knowledge on the crystal-electric field scheme of cerium, the case was further investigated based on degrees of freedom having both magnetic dipole and magnetic octupole components. These works agree towards a quantum spin ice (QSI)...
In the context of the EU Horizon project ACDC, we simulate the movement and agglomeration of oil droplets in water under constraints, like confinement, using a simplified stochastic-hydrodynamic model. In the analysis of the network created by the droplets in the agglomeration, we focus both on local and global structures and compare the computational results for various system sizes.
Nanopore-based resistive pulse sensing is an experimental technique that allows characterizing proteins on a single-molecule level. The signal from the nanopore depends on the characteristics of the pore, as well as the shape, volume, and orientation of the protein.
To investigate those current traces, we employed a machine learning algorithm trained on bead-model-based simulation data. Our...
Scanning probe microscopy (SPM) techniques are now routinely used to access information about the material on the level of individual atoms and molecules. Recent advances in quantum-based technology motivate their further evolution overcoming their present limitations. In our work, we explore the possibilities to enhance the SPM sensitivity to magnetic fields by decorating the probe apex with...
