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.
We study the electronic transport properties of weakly coupled 1µm-large quantum dots (QDs) defined in GaAs/AlGaAs-heterostructures in the integer and fractional quantum Hall regime. Between filling factor 2 > ν > 1, the Coulomb resonances observed in the current through the QD are modified whenever an electron tunnels between the two Landau levels. Additionally, we employ charge detection and...
Rigid tannin-furanic foams are porous materials synthetized from wood industry products, and have potential applications as new materials for green-building technology, and possibly also for waste water purification. Within the Interreg Italy-Austria ITAT1023 InCIMa project (2017-2019), foam samples synthetized under varying chemical conditions at the Salzburg University of Applied Sciences...
A detailed characterization of the mechanical performance, such as tensile strength, heat deflection temperature, compressive strength as well as impact strength, of 3D-printed wood-fiber-reinforced biocomposites was carried out as a function of various infill pattern orientations. Two wood filaments differing in terms of wood fiber content were utilized for specimen production, using a...
Magnetic three-dimensional structures on the nanoscale possess static and dynamic properties not found in their ‘flat’ counterparts. The recent development of three-dimensional lithography and probing techniques (such as X-ray tomography) has enabled the experimental investigation of such structures. Concurrently, simulations need to be developed to gain detailed understanding of the...
The investigation of quantum phenomena in solid state systems requires the ability to cool down macroscopic samples to low temperature. Lowering the temperature allows said quantum phenomena to develop and emerge in experiments. In semiconducting devices and at millikelvin temperatures, the cool down of an electron gas is increasingly challenging due to vanishing thermal conductivities and the...
We show that non-local orbits can arise in the presence of time-reversal symmetry (TRS), via full-lattice simulations of a system with four Weyl points subjected to an axial field [1,2]. Magnetic field, applied to a system with Weyl points, results in pseudo-Landau levels that disperse only along the field direction [3]. An appealing idea is to avoid breaking TRS, and rely on an axial field....
We present measurements of quantized conductance in a quantum point contact (QPC) defined entirely by electrostatic gating of a high-mobility InAs quantum well. Spin splitting is observed separately when applying a magnetic field in either parallel or perpendicular direction and in the latter case it is superimposed by magnetic depopulation. We resolve the energy levels of the QPC by finite...
We propose an exact construction for atypical excited states of a class of non-integrable quantum many-body Hamiltonians in one dimension (1D), two dimensions (2D), and three dimensions (3D) that display area law entanglement entropy. These examples of many-body “scar” states have, by design, other properties, such as
topological degeneracies, usually associated with the gapped ground states...
The orthorhombic (Pbnm) HoMnO3 is of particular interest due to its high magnetically-induced polarization values and magnetoelectric coupling strength. The high magnetic frustration results in a magnetic order that creates a distortion in the crystal lattice. This distortion breaks inversion symmetry and creates a macroscopic electric polarization P along the a-axis.
We investigated the...
Here, we present results of ultrasound investigations of the frustrated Tb$_2$Ti$_2$O$_7$. This cubic material features a Curie-Weiss temperature of $\theta_{\text{CW}} = - 19$ K, but no magnetic ordering has been detected down to 50 mK, indicating a large frustration factor.
Our ultrasound results evidence a strong spin-lattice coupling in Tb$_2$Ti$_2$O$_7$. We observed pronounced minima...
We present a method on how to calculate analitically the energy splitting between the two lowest levels of spin models on non-frustrated clusters in lowest-order degenerate perturbation theory. We apply it to arbitrary size 1D chains and small 2D and 3D clusters and find that by tunning an external magnetic field, the ground can be made degenerate on N different fields, where N is the number...
Layered transition metal dichalcogenides are intensively investigated due to their rich optoelectronic, superconducting and topological properties and their potential usage as mono-layer building blocks. Surprisingly, in semiconducting 2H-MoTe$_2$ long-range magnetic order of unknown origin has recently been observed [1]. Here we present the full 3D band structure of 2H-MoTe$_2$, determined...
We report the discovery of magnetic order in bulk semiconducting transition metal dichalcogenides (TMDs) 2H-MoTe2 and 2H-MoSe2 [1]. The muon spin rotation (muSR) measurements show the presence of long-range magnetic order in both compounds. DFT calculations show that this magnetism is promoted by the presence of defects in the crystal. The STM measurements show that the vast majority of...
Zinc oxide is a rather new material for optoelectronic applications. Due to its high LO phonon energy (ELO~72 meV), it is suitable for THz-devices like quantum cascade lasers (QCLs), which are currently limited to operation temperatures around ~200 K for typical GaAs material systems.
In this work, we show the development of a full fabrication process for double metal waveguides, processed...
We report magnetic investigations of a novel Kagome-related compound. Single crystals of the compound Cu2OSO4 have been studied by neutron scattering, magnetization and susceptibility. We find that instead of the spin-liquid ground state expected for a kagome compound, Cu2OSO4 orders in a canted anti-ferromagnetic structure. The magnetic structure is solved through neutron diffraction. The...
RNiO3 (R = trivalent rare earth ions) perovskites are a unique class of materials, where structural, electric and magnetic transitions are directly linked to the size of the incorporated rare earth ion. The transitions are temperature dependent, which allows a systematic study. Of special interest in this series is where the transition point reaches 0K, which creates a frustrated system...
We present an infrared spectroscopy study of ZrTe$_5$, which realizes a recent theoretical proposal that this material exhibits a temperature-driven topological quantum phase transition from a weak to a strong topological insulating state through an intermediate Dirac semimetal state around $T_p \simeq$ 138K. Our study details the temperature evolution of the energy gap in the bulk electronic...
The serial nature of a scanning probe microscope (SPM) renders data taking not only slow but may even prevent complex measurement tasks due to time limitations. Here we introduce the concept of compressed sensing (CS) as an effective sampling routine for SPM, requiring a significantly smaller subset of data points without compromising the measured information content. Our approach relies only...
The ability to resolve individual bonds within a single molecule represents one of the greatest feats of atomic force microscopy (AFM). The imaging mechanism is based on a functionalized tip that dynamically responds to tip-sample interactions. However, these interactions depend on a convolution of sample and tip that puts aspects of the tip's behavior into focus. Here we demonstrate how to...
The iron pnictides high Tc superconductors exhibit a rich phase diagram that is known for the close proximity of the superconducting (SC) and antiferromagnetic (AF) or commensurate spin-density-wave (SDW) orders. In the hole-doped Ba1-xNaxFe2As2 (BNFA) SDW develops a long-range order that competes with superconductivity and is accompanied by transitions between various structural and magnetic...
Crystal phase engineering in semiconductors has attracted considerable interest because of its potential applications in solid state lighting and group IV emitters. However, synthesizing materials in their thermodynamically less stable phase is challenging and so far, has mainly been realized in nanowires. Here, we present a general approach to controllably integrate both zinc-blende (ZB) and...
We study the generic dynamics of a special class of integrable periodically modulated quantum systems. Using conformal field theory and in particular a mapping to sine-square deformed field theories, we analytically obtain the full Floquet dynamics of a large class of conformal field theories. These integrable systems show both heating and non-heating phases. In our work, we explore the...
Particle size dependence of Tc and Hc in nanocrystalline (2-60 nm) BCC Tantalum was measured from electrical transport under magnetic field down to 50 mK. Both parameters show unexpected non-monotonic size dependence. Also, superconductivity is observed to persist for particle size even below the conventional estimate of Anderson limit. Again, when isolated Fe implants are embedded in Ta with...
In recent years it has been shown that electric fields in solids can be imaged, with sub-atomic resolution, using scanning transmission electron microscopy (STEM) and differential phase contrast imaging techniques. Here we use a Pauli equation based multislice method [Phys. Rev. Lett. 116, 127203 (2016)] to investigate the possibilities of imaging also microscopic magnetic fields with such...
Biologically-inspired computation schemes are more effective than standard digital-based approaches when dealing with complex, unstructured tasks as image recognition. In particular, systems of frequency-locked, coupled oscillators exhibit associative memory capabilities encoded in the phase difference of the signal. We are using oscillating neural networks as hardware accelerators for image...
The fast modulation characteristics of quantum cascade lasers (QCLs) up to the MHz-/GHz-range give insight into their dynamical properties and act as a prerequisite for QCL-based experiments like e.g. the injection locking of mid-infrared frequency combs, spectroscopic measurements or high data transmission optical free-space telecommunication applications. In this paper we present the first...
We present a homogeneous, bound-to-continuum Quantum Cascade Laser (QCL) featuring a spectral bandwidth up to 1.65 THz centered at 3.45 THz in a bi-stable CW lasing point above the typically not accessible NDR regime due to voltage driven operation. Below the NDR a spectral coverage of ~1 THz is observed with an electrically detected single and narrow beatnote indicating frequency comb...
Terahertz quantum cascade lasers based on double metal waveguides are compact sources of terahertz radiation with excellent properties in terms of covering a large bandwidth and exhibiting low waveguide dispersion. However, as the optical mode is confined to subwavelength dimensions, the emitted radiation produces a highly divergent far-field pattern. We designed and fabricated an antipodal...
Boron-containing III-V alloys have net yet been thoroughly characterized. Yet, the small lattice-constant of BAs enables applications in strain-engineering of nanowires. We report on the incorporation of B into self-catalyzed nanowires, grown by molecular beam epitaxy. Energy-dispersive X-ray spectroscopy scans in a scanning transmission electron microscope revealed a segregation of B atoms to...
A method for obtaining the dispersion of terahertz (THz) quantum cascade lasers (QCL) is presented. Previously shown in the mid-infrared (MIR) range, it involves measuring the relative phase of the center burst (0th order harmonic peak) and first satellite (1st order harmonic peak) from the interferogram of a THz QCL cavity, operated below threshold, emitting inside a Fourier Transform...
Underdoped cuprate high TC superconductors have been intensively studied, especially since the discovery of the pseudogap phenomenon in the 1990’s [1]. An important step towards the identification of the HTSC pairing mechanism was the discovery of a charge density wave (CDW) existing in large parts of the underdoped phase diagram [2-5]. In zero magnetic field (B=0) the short-ranged, static CDW...
The well-known Q-phase in CeCoIn5 is a rare example of cooperative coexistence of superconducting and magnetic order. For Nd0.05Ce0.95CoIn5, a second magnetic phase is stabilized at zero magnetic field with identical symmetry of Q-phase separated by a quantum critical point [1]. We present studies on 2% and 3.5% Nd-doped CeCoIn5 which interestingly shows that the SDW phase vanishes with...
CeCoIn5 is an intriguing d-wave superconductor with intertwined orders. A spin density wave exists only inside the superconducting phase [1], implying that superconductivity is an essential ingredient for the magnetic Q-phase. Its origin remain under debate. Since phonons couple to the electronic structure at MHz frequencies [2], ultrasound is suitable to investigate the properties of the...
NbS2 is a layered substance, which has recently shown great promise for building superconducting devices in the 2D limit [1,2]. While the layers consist of covalently bound atoms, weak van der Waals forces hold the layers together. NbS2 crystallises in two stable polymorphs, depending on the sulfur pressure during synthesis: the superconducting 2H phase and the metallic 3R phase[3–5].
We...
The functionalizing of downscaled solids by precise engineering of small defects, voids, porous structure and the amount, distribution and connectivity of such is a vibrant field of research and in demand of improved descriptors to successfully discriminate the increasing complexity. Positron Annihilation Spectroscopy (PAS) as a non-destructive method employing the unique sensitivity of the...
In this work we present the implementation of a sinusoidal modulation of the magnetic field to a Reflectance Difference Magneto-Optical Kerr Effect (RDMOKE) setup with increased sensitivity that allows detecting variations of the Kerr rotation angle below 1 μrad/mT at applied fields of a few mT. We illustrate the capabilities of the setup for Ni thin films grown on Cu(110)-(2x1)O surfaces that...
Interest in ferroelectric perovskites is due to their applications in electronics, and thin films are especially relevant. However, bulk properties, such as ferroelectricity itself, can be compromised at reduced scale. In this work, ferroelectric lead titanate (PTO) thin films are investigated.
Experimental (second harmonic generation) and computational (density functional theory) methods...
In this project we used X-ray Absorption Spectroscopy,X-ray Linear and Magnetic Circular Dichroism at the Mn $L_{3,2}$-edges to understand the ferromagnetic stability in $La_{0.7}Sr_{0.3}MnO_{3}$(LSMO) when interfaced with $SrRuO_{3}$(SRO),which is absent for the LSMO//$SrTiO_{3}$(STO).It has been proposed that charge transfer at the interface between LSMO and SRO allow the $dx^{2}-y^{2}$...
In the last years we established a new technology by using an in-house build STM in field emission regime. The emitter source (STM tip) is placed few nanometers away from the sample, where direct tunneling is suppressed. A part of the primary beam is backscattered (elastic and inelastic) from the sample and can escape the tip-target junction. The spin polarization of these electrons, which is...
The electronic properties of a hexagonal Boron Nitride (h-BN) monolayer on Pt(110) were investigated by ARUPS and compared to DFT-calculations. A work function change of about
-0.74 eV between the h-BN covered Pt(110) surface compared to pristine Pt(110) indicates a net charge transfer from h-BN to Pt. The measured electronic band structure is similar to previously reported band dispersions...
The interface effects in cuprate/manganite multilayers are the subject of many studies, which are focused not only on superconducting properties of antagonistic YBa2Cu3O7(YBCO), but also on its magnetic and electronic properties. In this study we will present our last investigations that proved that in Nd1-x(Ca1-ySry)xMnO3/YBCO/NCSMO (NYN) trilayers, the interfacial electron transfer and the...
With the aim of improving detection and analysis of Low-Energy and Secondary Electrons (LEEs and SEs of ≤100eV) in the Scanning Field-Emission Microscope (SFEM) tests are performed on a miniature electron detection unit employing a Bessel Box energy analyser. In electron microscopes, detection of LEEs is inherently difficult due to the presence of electrostatic (and magnetic) fields in...
The tangled processes involved in electron-induced Secondary Electron Emission (SEE), responsible for the generation of the ubiquitous Secondary Electrons in a solid surface, are discussed. The interaction of Low-Energy (LE) Electrons with diverse surfaces, of varying long-range order, was investigated by combining measurements of the Total Electron Yield, single-electron as well as...
A new solvent, formic acid, was used to fabricate sericin films. The effects of formic acid on the structural characteristics and mechanical properties of the sericin films were examined and compared with water. The gelation of sericin solution was retarded in formic acid compared to that of water. Sericin films cast from the formic acid exhibited a much higher crystallinity index than that...
Atomic parity violation experiments are one attempt to look for physics beyond the standard model. An
experiment to measure the atomic parity violation electric dipole contribution to the energy transition 7S1/2
and 6D3/2 in singly ionised Radium-226 is currently ongoing. The extraction of the atomic parity violating
signature for the measurement requires precise calculations based on...
Ultracold neutrons (UCN) with energies below 300 neV are storable for hundreds of seconds due to total reflection on the effective optical wall potential of the containment. They are used in experiments that benefit greatly from long measurement times, like the search for a permanent electric dipole moment of the neutron. The PSI UCN source makes use of solid deuterium as superthermal...
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) since May 2011 provides the opportunity to measure this composition in the energy range from ~0.2 GeV/n to ~10 GeV/n with unprecedented precision. For events...
Magnesium nuclei in cosmic rays are primary particles thought to be mainly produced and accelerated in astrophysical sources. Knowledge of the precise behavior of the Magnesium spectrum is important in understanding the origin, acceleration, and propagation of cosmic rays.
I will present the precision measurement of the Magnesium flux in the rigidity range from 3 GV to 3 TV based on data...
Understanding the precise rigidity dependence of the Silicon flux sheds light on the origin, acceleration and propagation of cosmic rays. I will present the precision measurement of the Silicon flux based on data collected by the Alpha Magnetic Spectrometer (AMS-02) during its first 7 years of operation on the International Space Station.
Muonic atom spectroscopy allows for a precise investigation of nuclear properties. At PSI we want to extract the nuclear charge radius of Radium-226 from its muonic x-ray spectrum. To measure the spectrum using only few µg of Radium-226 we have developed an apparatus in which the muons are stopped in a H2/D2 gas mixture and then diffuse towards a disk containing the Radium-226 nuclei. Monte...
The DARWIN Time Projection Chamber will be the most sensitive dark matter detector. The increased size of the detector over its precursors will raise new challenges. The DARWIN demonstrator, designed and to be built at the University of Zürich, will mainly be used to investigate the drift of electrons in liquid xenon over a distance of 2.6m, along with all the technological advances needed to...
DARWIN is a proposed next-generation xenon observatory that will be sensitive, among other rare interactions, to the neutrinoless double beta decay of 136Xe. Future experiments looking for this process will become more and more sensitive while the intrinsic radioactivity of the detector materials will be reduced thanks to the screening campaigns. This brings the risk that backgrounds...
For the neutron Beam EDM experiment at the University of Bern, a dedicated neutron detector has been supplied by the company CDT. The detector has been amply characterized in various aspects by taking data at the beamlines BOA and SANS-1at the Paul Scherrer Institute in September and December 2018. The results of these measurements in terms of efficiency, homogeneity, as well as wavelength and...
Lepton Flavour Universality (LFU) is one of the fundamental properties of the Standard Model: photon, W and Z bosons are predicted to be equally coupled to the three lepton generations. Hints for possible deviations from LFU have been found by the LHCb collaboration in $b\to s \ell \ell$ and $b\to c\ell\nu$ decays, sparking great interest.This poster explains the strategy adopted to study...
RADEM is a radiation monitor developed for ESA JUICE mission to icy moon of Jupiter: Ganymede, Callisto and Europa. Instrument contains of set of detectors optimized to measure electrons, protons, heavy ions and angular distributions of incoming radiation.
Assembling and qualification of Si-diode sensors for RADEM as well as test campaign of its Engineering Model were carried out at PSI....
The XENONnT experiment, projected to begin operation by early 2020 at the Laboratori Nazionali del Gran Sasso (LNGS), is a double-phase Time Projection Chamber with a 6 tonne liquid xenon target. Primarily developed to detect Weakly Interactive Massive Particles (WIMPs) that scatter of xenon nuclei, it will also be sensitive to neutrinos coming from a supernova burst beyond the edge of the...
XENONnT, the next stage in the XENON collaboration's search for dark matter, ist is an evolution of the very successful XENON1T experiment, which has set the strongest limits on various channels of WIMP-nucleus interactions and observed double-electron capture in $^{124}$Xe for the first time. A larger detector will mean a much-increased exposure and better self-shielding, giving sensitivity...
Antihydrogen studies aim to shed light on the observed baryon/antibaryon asymmetry in the Universe by comparing the properties of matter and antimatter with very high precision. In the context of the GBAR experiment located at CERN, our aim is to perform a measurement of the antihydrogen Lamb shift with an uncertainty of 100 ppm, which allows extracting the antiproton charge radius at a level...
The SHiP experiment is a beam dump experiment proposed at the CERN SPS aiming at the observation of long lived particles very weakly coupled with matter and at the study of tau-neutrino properties. Hidden particles are mostly produced in the decay of charmed hadrons and tau neutrinos are produced by Ds decays, therefore measuring charm production cross-sections from 400 GeV protons is critical...
NoMoS, the neutron decay products momentum spectrometer, investigates
the beta decay of the free neutron. It uses the R×B drift effect in a uniformly
curved magnetic field and a spatially resolving detector to separate and measure
the charged decay particles according to their momentum. The protons from
the decay are low energetic and need to be made detectable, therefore...
The observation of interference phenomena in two-dimensional mesoscopic systems is difficult, and so far constrained to graphene, where certain mechanisms originating in the graphene band structure strengthen the emergence of this phenomenon. Here, we report on the experimental observation of Fabry-Pérot oscillations in electrostatically defined cavities in InAs/GaSb quantum wells. Carriers...
The last decades have seen significant advances in coherence times of superconducting qubits. This was mainly made possible by reducing charge dispersion of transmon qubits, better thermalization and filtering of the readout and control circuitry as well as improvements in Josephson junction fabrication. Lately, efforts are being made in order to investigate limitations of coherence due to...
Fast and accurate two-qubit gates are a key requirement to perform complex algorithms on current quantum computers. Typical gates have errors less than 5% and take around 200ns. Shorter gates result in unwanted leakage out of the computational subspace. Optimal control theory aims to design fast control pulses that suppress side effects such as cross talk and leakage. However, even with an...
This poster studies the entanglement of two and three spin 1/2 particles in (special) relativistic settings, in particular for inertial observers at rest relatively to the entangled particles and in a Lorentz-boosted frame.
Here spin and momentum degrees of freedom of the particles can be viewed as 4-qubit and 6-qubit states, respectively. These states are analysed in terms of their...
The oscillation of neutrinos was predicted in the mid of the last century. Since then they were intensively studied both theoretically and experimentally since a couple of phenomena like e.g CP violation (charge-conjugation-parity) are conjectured. Also, it is not known which neutrino is the heaviest, formulated as the mass hierarchy problem. I will focus on how tools from foundations of...
We implement a single electron charge qubit in a gate defined linear triple dot array on a GaAs/AlGaAs heterostructure [1,2]. The qubit is strongly dipole-coupled to photons in a high impedance frequency tunable superconducting resonator. We operate the qubit at a higher order sweet spot along one of the detuning axes. Measuring the qubit coherence for different qubit configurations we acquire...
Distributing a secret to many parties such that none alone can reveal it was first proposed by Shamir (1979) and applied in the quantum scheme by Hillery, Bužek and Berthiaume (1999). By a modification of this HBB protocol Hiesmayr, Huber and Schauer showed that the security against eavesdropping or a dishonest party can be based on the physical property due to entanglement, more precise...
We explore theoretically the behavior of two coupled nonlinear photonic cavities, in presence of inhomogeneous coherent driving and local dissipations. By solving numerically the quantum master equation, we extrapolate the properties of the system in a well defined thermodynamical limit of large photon occupation. We focus on the peculiar regime where the mean field Gross-Pitaevskii approach...
The recently developed theory of entangled two-photon absorption (ETPA) predicts a linear dependence of its rate on the entangled pair flux in the low-power regime, and provides a tool for two-photon studies even on sensitive samples. We experimentally observed this signature for ETPA-induced fluorescence of Rhodamine 6G and its dependence on inter-photon delay, concentration and polarization...
Nanomechanical resonators with high quality factors and noise isolation are promising candidates for pushing the frontiers of magnetic resonance force microscopy towards single-spin detection. Single spin detection using state-of-the-art MRFM is hampered by the intrinsic weakness of the kHz-range signal and its frequency mismatch with the MHz-range resonators used to detect it. An alternate...
We present the coupling of a trapped ion to a nanomechanical oscillator/nanowire in order to study new methods for the preparation of complex motional quantum states that might be challenging to produce by conventional optical means. The quantum dynamics of such a hybrid system have been studied theoretically showing possibilities of creating coherent states, as well as purely non-classical...
The application of quantum-logic techniques to the spectroscopy of trapped molecular ions has enabled the determination of molecular properties at unprecedented levels of precision. Molecules have been proposed as suitable candidates for testing possible time-variation of fundamental constants and precision testing of QED. Further advancement in the measurement accuracy will be enabled through...
Discrete time crystals are a many-body state of matter where time translation symmetry is spontaneously broken in a periodically driven system. In view of the intense debate regarding the minimal requirements for the realization of a discrete time crystal, here we present a very pedagogical example of a many-body time crystal using coupled parametric resonators. We use classical bifurcation...
We create exciton-polariton condensates in engineered potential landscapes at room temperature by optically exciting a ladder-type conjugated polymer placed inside a tunable optical microcavity. In the upper mirror of the cavity we define multiple in-plane structures (from single defects to lattices). By exciting the system above threshold, we observe polariton condensation. Condensation...
We propose a triply-resonant electro-optic modulator as an efficient stationary source of entangled microwave and optical radiation, based on a mm-sized high optical $Q$ lithium niobate whispering gallery mode resonator (WGMR) coupled to a superconducting 3D microwave cavity. The creation of entangled microwave and optical photons is possible via spontaneous parametric down conversion (SPDC)...
Interfaces between stationary and traveling qubits are fundamental building blocks for quantum networks. Cavities are an established approach for an efficient interface; here, we use a fiber cavity to couple trapped ions to photons. Fiber cavities enable access to the strong coupling regime, allowing quantum communication to be carried out over long distances with high fidelity and efficiency....
Integrated photonic sources represent a key building block as practical, low-cost, schemes for quantum communication. In the context of photon pair sources, microring-resonators (MRR) are emerging as a viable solution for integrated photon pair sources with advantages for multiplexing and high dimensional entanglement generation.
By exploiting MRR as a photon pair source, sequential time-bin...
Solid-state electronic spins are promising candidates for various applications in quantum information science, such as quantum communication and computation. However, due to their strong magnetic dipoles they are quite susceptible to magnetic noise, which usually limits their coherence lifetimes. Here we demonstrate the storage of a 100 ns optical pulse in a 171Yb3+:Y2SO5 paramagnetic crystal...
Exploiting the band-gap induced by perpendicular electric fields, charge carriers in bilayer graphene can be confined via electrostatic gating. This realization provides a versatile and tunable platform hosting carbon-qubits.
We confine charge carriers to a narrow channel, defined by lateral gating. Another layer of gates, perpendicular to the transport direction, locally tune the carrier...
The accuracy of time information generated by clocks can be enhanced by allowing them to communicate with each other. Here we consider a basic scenario where a quantum clock receives a low-accuracy time signal as input and ask whether it can generate an output of higher accuracy. We propose protocols that, using a clock with a d-dimensional state space, achieve an accuracy enhancement by a...
The truncated classical coupled cluster (CC) methods have been known to provide non-variational energies in the systems that present multiconfigurational nature of the ground state. Methods such as paired CC (pCC) and singlet CC (CC0) unreliably correct this failure by eliminating excitations in the cluster operator.
In this work, we show that their unitary implementation (q-pUCC, q-UCC0) on...
In our experiment, we inductively couple a mechanical oscillator to a microwave circuit. Our magnetic cantilever leads to a position dependent magnetic field. This field is coupled to a microwave resonator via an embedded SQUID i.e. the resonance frequency depends on flux and consequently on the position of the cantilever.
Our first devices indicate a single photon coupling strength of up to...
We numerically study a weakly-interacting, harmonically-trapped boson gas coupled to a high-finesse optical cavity. The bosons self-organise into a lattice when the driving laser is strong enough. When the cavity is blue-detuned, we observe dimerization of lattice sites which leads to states with different atomic correlations. With an even stronger pumping laser, the system is driven into...
The loss of qubits - the elementary carriers of quantum information - poses one of the fundamental obstacles towards large-scale and fault-tolerant quantum information processors. We demonstrate an experimental toolbox for ion-qubit control and implement a full cycle of qubit-loss detection and correction on a minimal instance of the topological surface code. This includes a quantum...
TaAs has been predicted to be a Weyl semimetal with a complex Fermi surface composed of two Weyl and one trivial hole pocket. It is not evident how to describe the low energy excitations. In order to reveal the details of the low energy electronic band structures of TaAs, we performed reflectivity measurements at zero field at various temperatures, as well as magneto-optical spectroscopy up to...
3D Dirac and Weyl semimetals are the analogs of graphene which possess 3D linear dispersion around points in the Brilloun zone. Optical and transport studies are widely used in order to explore these compound. TaIrTe$_4$ is expected to be a Weyl semimetals that have the fewest Weyl points - 4 - in comparison to TaAs, which contains 12 pairs. It has been theoretically shown that TaIrTe$_4$...
The Bilinear-Biquadratic spin-1 chain (BLBQ) has been studied for its entangled ground states, diverse phases and topological properties. The natural language to study entanglement in strongly correlated systems is tensor networks. Using time dependent tensor network simulations, we demonstrate the dynamical spin and quadrupolar structure factors of the BLBQ model in ferroquadrupolar dimer...
Suspended Bernal-stacked graphene multilayers exhibit a broken-symmetry ground state whose origin remains to be understood. Based on electrical transport measurements, we observe a second-order phase transition, whose critical temperature ($T_C$) increases a function of the thickness of the system, starting from 12K in bilayer up to 100K in heptalayer devices. Furthermore, by means of a...
Crystal defects in topological insulators (TIs) are known to bind anomalous electronic states with two fewer dimensions than the bulk; the most commonly cited examples are the helical modes bound to screw dislocations in weak TIs. In this talk, we extend the classification of topological electronic defect states. By mapping the Hamiltonians of planes in momentum space to the real-space...
We investigate and compare few-particle one-dimensional bosonic and fermionic gases with infi?nite-range interactions induced by a laser-driven dissipative optical cavity by computing density distributions and correlation functions. With increasing cavity-atom coupling, both types of gases self-organize into a one-dimensional lattice structure with diff?erent site occupations. As the...
Deterministic control of the intrinsic polarisation state of ferroelectric thin films is essential for devises applications. Additionally to the now well-established role of electrostatic boundary condition and epitaxial strain, we show also the importance of Pb-O divacancy gradients. We report on the full control of the polarisation orientation of ferroelectric thin films through changes in...
Nodal-line semimetals offer a unique setting for novel transport phenomena. With weak disorder, the torus-shaped Fermi surface and encircled π Berry flux carried by the nodal loop generate a fascinating interplay between the effective dimensionality of electron diffusion and band topology, which depends on the scattering range of the impurity potential relative to the size of the nodal loop....
CaAlSi and SrAlSi are ternary superconductors that crystallize in AlB2-type structures with critical temperatures of Tc = 8 K, and 5 K, respectively. They surprisingly differ in properties among each other although they have similar electronic structures, and only a small difference in their crystallographic structures. We have in a systematic approach analyzed the Ca1-xSrxAlSi solid solution...
We report on the synthesis and the superconductivity of the h-carbide type oxides Zr4Rh2Ox (x = 0.7, 1.0). Detail physical measurements show that they are strongly type-II bulk superconductors with critical temperatures of Tc ≈ 2.8 K and 4.7 K in the resistivity, respectively. Our results support that the h-carbide compounds are a versatile family of compounds for the investigation of the...
The chiral-lattice ferrimagnet Cu2OSeO3 has been evidenced to exhibit a second skyrmion phase stabilized by cubic anisotropy well below 57K. It is particularly interesting when aiming at an experimental investigation of magnon band structures in skyrmion lattices and their potential application for microwave devices operating at GHz frequencies. We explored spin excitations in a Cu2OSeO3...
Due to their promising technological applications, magnetic Skyrmions in Chiral magnets, such as Cu$_2$OSeO$_3$, have been the center of attention of the scientific community. By manipulating the crystallite size in the range of a single Skyrmion (62nm), it could be interesting to see if the magnetic phase diagram can be tuned. We have employed solution growth techniques to have controllable...
Skyrmions are topologically protected nanometer-sized magnetic vortices interesting for spintronics applications. Current challenges lie in the discovery and synthesis of materials with high critical temperatures ($T_c$) and their implementation in thin-film technology. Here we present an approach for strain-free epitaxial thin-film growth of near-room temperature skyrmion-hosting material...
Cobalt-based layered perovskites have emerged as promising electrocatalysts for the oxygen evolution reaction (OER), but fundamental questions regarding the design principles for highly active perovskite electrocatalysts are still open. A recent study demonstrated that oxygen vacancies play a critical role in the OER mechanism and on the perovskite electrochemical activity.
Double perovskite...
In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets with spiral magnetic orders. Such materials are of high current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low magnetic order temperatures (typically < 100 K) greatly restrict their fields of...
Spin-rotation coupling is an extension of the Sagnac effect, based upon the inertia of intrinsic spin. To confirm its existence, a neutron interferometer experiment was proposed [1,2] coupling the spin to the rotation of a magnetic field. The results of a neutron polarimeter experiment comply with the prediction but can also be explained semi-classically.
A spin manipulator for a respective...
The sensitivity of 3D magnetohydrodynamical equilibria to the toroidal current profile is of paramount importance for stellarator optimization and operation. In fact, magnetic field-line chaos can emerge depending on the plasma pressure and currents, thereby strongly affecting particle confinement. The Stepped-Pressure Equilibrium Code (Hudson et al., Phys. Plasmas, vol 19 (11), 2012) can be...
Electron-Cyclotron waves are an important tool in tokamak devices for core heating, current drive and MHD mode stabilization. Density fluctuations at the edge can cause a broadening of the EC beam before absorption, potentially leading to inaccurate or less efficient power deposition, especially in large tokamak devices. This can be modeled with the quasilinear Fokker-Planck code LUKE, using a...
With the misuse of antibiotics, antimicrobial resistance becomes a very serious public health issue. Proposed technique of antibiotic sensitivity characterization is based on the bacterial nanomotion. The organism of interest is attached onto a cantilever and nanoscale movements induce cantilever oscillations. If the organism is exposed to an antibiotic to which it is sensitive, the...
We simulate how droplets released from a linear droplet generator arrange themselves in a three-dimensional way within a surrounding hull. During this arrangement process, droplets touching each other can form bilayers, which then can be broken up and reformed again. For studying this process, we perform macroscale Monte Carlo movement simulations with a simplified rule set for the slowing...
Hydrodynamic electron transport has recently been observed in the Weyl semi-metal tungsten diphosphide (WP2). However, manufacturing microdevices from single crystals is very challenging. Here, focused ion beam (FIB) milling is used to pattern and contact microstructures of WP2 aiming to achieve precise device geometries and lowest contact resistances, which is important for accurate...
