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Centrosymmetric compounds which host three-dimensional topological spin structures comprise a distinct subclass of materials in which multiple-q magnetic order is stabilized by anisotropy and bond frustration in contrast to the more common path of antisymmetric exchange interactions. Here we investigate static and dynamic magnetic properties of the cubic perovskite SrFeO_{3}—a rare example of a centrosymmetric material hosting two types of topological spin textures: skyrmionlike and hedgehog-lattice phases. Our detailed magnetization and dilatometry measurements describe the domain selection processes and phase transitions in SrFeO_{3}. Spin excitations are investigated using inelastic neutron scattering for all three zero-field phases. In the higher-temperature ordered phases, high-energy magnons increasingly lose coherence, so that spin fluctuations are dominated by a distinct quasielastic component at low energies. We anticipate that this could be generic to symmetric helimagnets in which the chiral symmetry is spontaneously broken by the magnetic order. more...

Using time- and angle-resolved photoemission spectroscopy, we examine the unoccupied electronic structure and electron dynamics of the type-I Weyl semimetal PtBi_{2}. Using the ability to change the probe photon energy over a wide range, we identify the predicted Weyl points in the unoccupied three-dimensional band structure and we discuss the effect of k_{⊥} broadening in the normally unoccupied states. We characterize the electron dynamics close to the Weyl points and in other parts of three-dimensional Brillouin zone using k-means, an unsupervised machine-learning technique. This reveals distinct differences—in particular, that the electron dynamics close to the Weyl points are slower than in Brillouin zone regions close to the bulk Fermi surface. more...

This study evaluated the effectiveness and usage of a smartphone application for adjusting the hearing impression of cochlear implants or hearing aids in everyday contexts. Building on previous laboratory research that demonstrated subjective auditory perception improvements through personalized settings, this research aimed to confirm these findings in real-life scenarios. Additionally, it analyzes user behavior and adaptation practices. Over a period of six months, 15 participants, including both bimodal and bilateral cochlear implant recipients, employed a self-adjustment app in their everyday lives. This application enabled them to modify the auditory experience through two distinct user interfaces and store their configurations as accessible programs. The collected data indicated that all participants were able to operate the app, and 13 of 15 participants successfully used the app throughout the whole study. In contrast to our previous findings, the acoustic environment did not affect frequency settings but did influence the choice of user interface. Bimodal users more frequently adjusted the settings for each ear independently compared to bilateral users. Most participants stated that they would also use the app outside of this study. more...

Abstract The field of nanowire (NW) technology represents an exciting and steadily growing research area with applications in ultra-sensitive mass and force sensing. Existing detection methods for NW deflection and oscillation include optical and field emission approaches. However, they are challenging for detecting small diameter NWs because of the heating produced by the laser beam and the impact of the high electric field. Alternatively, the deflection of a NW can be detected indirectly by co-resonantly coupling the NW to a cantilever and measuring it using a scanning probe microscope. Here, we prove experimentally that co-resonantly coupled devices are sensitive to small force derivatives similar to standalone NWs. We detect force derivatives as small as 10−9 N/m with a bandwidth of 1 Hz at room temperature. Furthermore, the measured hybrid vibration modes show clear signatures of avoided crossing. The detection technique presented in this work verifies a major step in boosting NW-based force and mass sensing. more...

A quantitative magnetic force microscopy technique is presented that maps one magnetic stray-field component and its spatial derivative at the same time. Furthermore, this technique is applied to investigate individual circular magnetic nano-domains in MnNiGa bulk samples providing bubble diameters and the spatial extent in depth. more...

Observations of the anomalous Hall effect in RuO2 and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe, the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO2 is excluded by symmetry for the Néel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the Néel vector from the easy-axis toward the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO2 thin-film samples, whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field Hc ≃ 55 T that was inaccessible in earlier studies but is consistent with the expected Néel-vector reorientation field. more...

Inducing a magnetic gap at the Dirac point of the topological surface state (TSS) in a three-dimensional (3D) topological insulator (TI) is a route to dissipationless charge and spin currents. Ideally, magnetic order is present only at the surface, as through proximity of a ferromagnetic (FM) layer. However, experimental evidence of such a proximity-induced Dirac mass gap is missing, likely due to an insufficient overlap of TSS and the FM subsystem. Here, we take a different approach, namely ferromagnetic extension (FME), using a thin film of the 3D TI Bi_{2}Te_{3}, interfaced with a monolayer of the lattice-matched van der Waals ferromagnet MnBi_{2}Te_{4}. Robust 2D ferromagnetism with out-of-plane anisotropy and a critical temperature of T_{c}≈15 K is demonstrated by x-ray magnetic dichroism and electrical transport measurements. Using angle-resolved photoelectron spectroscopy, we observe the opening of a sizable magnetic gap in the 2D FM phase, while the surface remains gapless in the paramagnetic phase above T_{c}. Ferromagnetic extension paves the way to explore the interplay of strictly 2D magnetism and topological surface states, providing perspectives for realizing robust quantum anomalous Hall and chiral Majorana states. more...

The quest for a half-quantized thermal Hall effect of a Kitaev system represents an important tool to probe topological edge currents of emergent Majorana fermions. Pertinent experimental findings for α-RuCl_{3} are, however, strongly debated, and it has been argued that the thermal Hall signal stems from phonons or magnons rather than from Majorana fermions. Here, we investigate the thermal Hall effect of the Kitaev candidate material Na_{2}Co_{2}TeO_{6}, and we show that the measured signal emerges from at least two components, phonons and magnetic excitations. This dichotomy results from our discovery that the longitudinal and transversal heat conductivities share clear phononic signatures, while the transversal signal changes sign upon entering the low-temperature, magnetically ordered phase. Our results demonstrate that uncovering a genuinely quantized magnetic thermal Hall effect in Kitaev topological quantum spin liquids such as α-RuCl_{3} and Na_{2}Co_{2}TeO_{6} requires disentangling phonon vs magnetic contributions, including potentially fractionalized excitations such as the expected Majorana fermions. more...

The nematicity in multilayer FeSe/SrTiO_{3} films has been previously suggested to be enhanced with decreasing film thickness. Motivated by this, there have been many discussions about the competing relation between nematicity and superconductivity. However, the criterion for determining the nematicity strength in FeSe remains highly debated. The understanding of nematicity as well as its relation to superconductivity in FeSe films is therefore still controversial. Here, we fabricate multilayer FeSe/SrTiO_{3} films using molecular beam epitaxy and study the nematic properties by combining angle-resolved photoemission spectroscopy, ^{77}Se nuclear magnetic resonance, and scanning tunneling microscopy experiments. We unambiguously demonstrate that, near the interface, the nematic order is suppressed by the SrTiO_{3}-induced tensile strain; in the bulk region further away from the interface, the strength of nematicity recovers to the bulk value. Our results not only solve the recent controversy about the nematicity in multilayer FeSe films, but also offer valuable insights into the relationship between nematicity and superconductivity. more...

Smartphones are increasingly being used to enable patients to play an active role in managing their own health through applications, also called apps. The latest generation of sound processors for cochlear implants offer Bluetooth connectivity that makes it possible to connect smartphones or tablets and thus enable patients to modify their hearing sensation or measure system parameters. However, to achieve a high adoption rate and secure operation of these applications, it is necessary to design intuitive user interfaces (UI) for end users. The main goal of the current study was to evaluate the usability of two different UIs. A second goal was to compare the hearing outcomes based on the patient’s adjustments. The two different UIs were explored in a group of adult and older adult bimodal cochlear-implant users, with adjustments possible for both the cochlear implant and the contralateral hearing aid. One of the UIs comprised a classical equalizer and volume-dial approach, while the second UI followed a 2D-Surface concept, to manipulate the corresponding sound parameters. The participants changed their fitting parameters using both UIs in seven different sound scenes. The self-adjusted settings for the different scenarios were stored and recalled at a later stage for direct comparison. To enable an assessment of reliability and reproducibility, the self-adaptation was also repeated for two of the seven sound scenes. Within minutes, the participants became accustomed to the concept of both UIs and generated their own parameter settings. Both UIs resulted in settings that could be considered similar in terms of spontaneous acceptance and sound quality. Furthermore, both UIs showed high reliability in the test–retest procedure. The time required for adjustment was significantly shorter with the 2D-Surface UI. A closer look at the bimodal aspect shows that participants were able to compensate for differences in loudness and frequencies between the cochlear implant and the hearing aid. The blind comparison test showed that self-adjustment led to a higher acceptance of the sound perception in more than 80% of the cases. more...

Cr_{2}Ge_{2}Te_{6} is a quasi-two-dimensional semiconducting van der Waals ferromagnet down to the bilayer with great potential for technological applications. Engineering the critical temperature to achieve room-temperature applications is one of the critical next steps on this path. Here, we report high-resolution capacitance dilatometry studies on Cr_{2}Ge_{2}Te_{6} single crystals which directly prove significant magnetoelastic coupling and provide quantitative values of the large uniaxial pressure effects on long-range magnetic order (∂T_{C}/∂p_{c}=24.7 K/GPa and ∂T_{C}/∂p_{ab}=−15.6 K/GPa) derived from thermodynamic relations. Moderate in-plane strain is thus sufficient to strongly enhance ferromagnetism in Cr_{2}Ge_{2}Te_{6} up to room temperature. Moreover, unambiguous signs of short-range magnetic order up to 200 K are found. more...

Nematicity in heavily hole-doped iron pnictide superconductors remains controversial. Sizeable nematic fluctuations and even nematic orders far from magnetic instability were declared in RbFe2As2 and its sister compounds. Here, we report a systematic elastoresistance study of a series of isovalent- and electron-doped KFe2As2 crystals. We found divergent elastoresistance on cooling for all the crystals along their [110] direction. The amplitude of elastoresistivity diverges if K is substituted with larger ions or if the system is driven toward a Lifshitz transition. However, we conclude that none of them necessarily indicates an independent nematic critical point. Instead, the increased nematicity can be associated with another electronic criticality. In particular, we propose a mechanism for how elastoresistivity is enhanced at a Lifshitz transition. more...

We report the superconducting properties of the Co2Cr1−xFexAly/Cu/Ni/Cu/Pb spin-valve structure the magnetic part of which comprises the Heusler alloy layer HA = Co2Cr1−xFexAly with a high degree of spin polarization (DSP) of the conduction band and a Ni layer of variable thickness. The separation between the superconducting transition curves measured for the parallel (α = 0°) and perpendicular (α = 90°) orientation of the magnetization of the HA and the Ni layers reaches up to 0.5 K (α is the angle between the magnetization of two ferromagnetic layers). For all studied samples the dependence of the superconducting transition temperature Tc on α demonstrates a deep minimum in the vicinity of the perpendicular configuration of the magnetizations. This suggests that the observed minimum and the corresponding full switching effect of the spin valve is caused by the long-range triplet component of the superconducting condensate in the multilayer. Such a large effect can be attributed to a half-metallic nature of the HA layer, which in the orthogonal configuration efficiently draws off the spin-polarized Cooper pairs from the space between the HA and Ni layers. Our results indicate a significant potential of the concept of a superconducting spin-valve multilayer comprising a half-metallic ferromagnet, recently proposed by A. Singh et al., Phys. Rev. X 2015, 5, 021019, in achieving large values of the switching effect. more...

We have experimentally determined the momentum dependence of the electronic excitation spectra of para-quaterphenyl single crystals. The parallel arrangement of para-quaterphenyl molecules results in a strong Coulomb coupling of the molecular excitons. Such crystals have been considered to be a very good realization of the Frenkel exciton model, including the formation of H-type aggregates. Our data reveal an unexpected exciton dispersion of the upper Davydov component, which cannot be rationalized in terms of inter-molecular Coulomb coupling of the excitons. A significant reduction of the nearest neighbor coupling due to additional charge-transfer processes is able to provide an explanation of the data. Furthermore, the spectral onset of the excitation spectrum, which represents a heavy exciton resulting from exciton–phonon coupling, also shows a clear dispersion, which had been unknown so far. Finally, an optically forbidden excitation about 1 eV above the excitation onset is observed. more...

Atomically thin transition metal dichalcogenides (TMDCs) are promising candidates for implementation in next generation semiconducting devices, for which laterally homogeneous behavior is needed. Here, we study the electronic structure of atomically thin exfoliated WSe2, a prototypical TMDC with large spin–orbit coupling, by photoemission electron microscopy, electron energy-loss spectroscopy, and density functional theory. We resolve the inhomogeneities of the doping level by the varying energy positions of the valence band. There appear to be different types of inhomogeneities that respond differently to electron doping, introduced by potassium intercalation. In addition, we find that the doping process itself is more complex than previously anticipated and entails a distinct orbital and thickness dependence that needs to be considered for effective band engineering. In particular, the density of selenium vs tungsten states depends on the doping level, which leads to changes in the optical response beyond increased dielectric screening. Our work gives insight into the inhomogeneity of the electron structure of WSe2 and the effects of electron doping, provides microscopic understanding thereof, and improves the basis for property engineering of 2D materials. more...

We have studied superconducting properties of spin-valve thin-layer heterostructures CoOx/F1/Cu/F2/Cu/Pb in which the ferromagnetic F1 layer was made of Permalloy while for the F2 layer we have taken a specially prepared film of the Heusler alloy Co2Cr1−xFexAl with a small degree of spin polarization of the conduction band. The heterostructures demonstrate a significant superconducting spin-valve effect, i.e., a complete switching on and off of the superconducting current flowing through the system by manipulating the mutual orientations of the magnetization of the F1 and F2 layers. The magnitude of the effect is doubled in comparison with the previously studied analogous multilayers with the F2 layer made of the strong ferromagnet Fe. Theoretical analysis shows that a drastic enhancement of the switching effect is due to a smaller exchange field in the heterostructure coming from the Heusler film as compared to Fe. This enables to approach an almost ideal theoretical magnitude of the switching in the Heusler-based multilayer with a F2 layer thickness of ca. 1 nm. more...

The electronic structures of the iron-based superconductors have been intensively studied by using angle-resolved photoemission spectroscopy (ARPES). A considerable amount of research has been focused on the LaFeAsO family, showing the highest transition temperatures, where previous ARPES studies have found much larger Fermi surfaces than bulk theoretical calculations would predict. The discrepancy has been attributed to the presence of termination-dependent surface states. Here, using photoemission spectroscopy with a sub-micron focused beam spot (nano-ARPES) we have successfully measured the electronic structures of both the LaO and FeAs terminations in LaFeAsO. Our data reveal very different band dispersions and core-level spectra for different surface terminations, showing that previous macro-focus ARPES measurements were incomplete. Our results give direct evidence for the surface-driven electronic structure reconstruction in LaFeAsO, including formation of the termination-dependent surface states at the Fermi level. This experimental technique, which we have shown to be very powerful when applied to this prototypical compound, can now be used to study various materials with different surface terminations. more...

Single crystals of pristine and 6% Pd-intercalated 2H‐TaSe _2 have been studied by means of ^77 Se nuclear magnetic resonance. The temperature dependence of the ^77 Se spectrum, with an unexpected line narrowing upon Pd intercalation, unravels the presence of correlated local lattice distortions far above the transition temperature of the charge density wave (CDW) order, thereby supporting a strong-coupling CDW mechanism in 2H‐TaSe _2 . While, the Knight shift data suggest that the incommensurate CDW transition involves a partial Fermi surface gap opening. As for spin dynamics, the ^77 Se spin-lattice relaxation rate ${T}_{1}^{-1}$ as a function of temperature shows that a pseudogap behavior dominates the low-energy spin excitations even within the CDW phase, and gets stronger along with superconductivity in the Pd-6% sample. We discuss that CDW fluctuations may be responsible for the pseudogap as well as superconductivity, although the two phenomena are unlikely to be directly linked each other. more...

In the present work, we demonstrate different synthesis procedures for filling carbon nanotubes (CNTs) with equimolar binary nanoparticles of the type Fe–Co. The CNTs act as templates for the encapsulation of magnetic nanoparticles and provide a protective shield against oxidation as well as prevent nanoparticle agglomeration. By variation of the reaction parameters, we were able to tailor the sample purity, degree of filling, the composition and size of the filling particles, and therefore, the magnetic properties. The samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), superconducting quantum interference device (SQUID) and thermogravimetric analysis (TGA). The Fe–Co-filled CNTs show significant enhancement in the coercive field as compared to the corresponding bulk material, which make them excellent candidates for several applications such as magnetic storage devices. more...

For future molecular spintronic applications the possibility to modify and tailor the magnetic properties of transition-metal complexes is very promising. One of such possibilities is given by the countless derivatization offered by carbon chemistry. They allow for altering chemical structures and, in doing so, to tune magnetic properties of molecular spin-carrying compounds. With emphasis on the interplay of the spin density distribution of mononuclear and magnetic superexchange couplings of trinuclear bis(oxamato)-type complexes we review on efforts on such magneto-structural correlations. more...

Manganese phthalocyanine (MnPc) is a member of the family of transition-metal phthalocyanines, which combines interesting electronic behavior in the fields of organic and molecular electronics with local magnetic moments. MnPc is characterized by hybrid states between the Mn 3d orbitals and the π orbitals of the ligand very close to the Fermi level. This causes particular physical properties, different from those of the other phthalocyanines, such as a rather small ionization potential, a small band gap and a large electron affinity. These can be exploited to prepare particular compounds and interfaces with appropriate partners, which are characterized by a charge transfer from or to MnPc. We summarize recent spectroscopic and theoretical results that have been achieved in this regard. more...

We performed a study on the fundamental adsorption characteristics of Er3N@C80 deposited on W(110) and Au(111) via room temperature scanning tunneling microscopy and spectroscopy. Adsorbed on W(110), a comparatively strong bond to the endohedral fullerenes inhibited the formation of ordered monolayer islands. In contrast, the Au(111)-surface provides a sufficiently high mobility for the molecules to arrange in monolayer islands after annealing. Interestingly, the fullerenes modify the herringbone reconstruction indicating that the molecule–substrate interaction is of considerable extent. Investigations concerning the electronic structure of Er3N@C80/Au(111) reveals spatial variations dependent on the termination of the Au(111) at the interface. more...

We have investigated with the pulsed ESR technique at X- and Q-band frequencies the coherence and relaxation of Cu spins S = 1/2 in single crystals of diamagnetically diluted mononuclear [n-Bu4N]2[Cu(opba)] (1%) in the host lattice of [n-Bu4N]2[Ni(opba)] (99%, opba = o-phenylenebis(oxamato)) and of diamagnetically diluted mononuclear [n-Bu4N]2[Cu(opbon-Pr2)] (1%) in the host lattice of [n-Bu4N]2[Ni(opbon-Pr2)] (99%, opbon-Pr2 = o-phenylenebis(N(propyl)oxamidato)). For that we have measured the electron spin dephasing time Tm at different temperatures with the two-pulse primary echo and with the special Carr–Purcell–Meiboom–Gill (CPMG) multiple microwave pulse sequence. Application of the CPMG protocol has led to a substantial increase of the spin coherence lifetime in both complexes as compared to the primary echo results. It shows the efficiency of the suppression of the electron spin decoherence channel in the studied complexes arising due to spectral diffusion induced by a random modulation of the hyperfine interaction with the nuclear spins. We argue that this method can be used as a test for the relevance of the spectral diffusion for the electron spin decoherence. Our results have revealed a prominent role of the opba4– and opbon-Pr24– ligands for the dephasing of the Cu spins. The presence of additional 14N nuclei and protons in [Cu(opbon-Pr2)]2– as compared to [Cu(opba)]2– yields significantly shorter Tm times. Such a detrimental effect of the opbon-Pr24− ligands has to be considered when discussing a potential application of the Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes as building blocks of more complex molecular structures in prototype spintronic devices. Furthermore, in our work we propose an improved CPMG pulse protocol that enables elimination of unwanted echoes that inevitably appear in the case of inhomogeneously broadened ESR spectra due to the selective excitation of electron spins. more...

The reaction of one equivalent of [n-Bu4N]2[Ni(opboR2)] with two equivalents of [Cu(pmdta)(X)2] afforded the heterotrinuclear CuIINiIICuII containing bis(oxamidato) type complexes [Cu2Ni(opboR2)(pmdta)2]X2 (R = Me, X = NO3– (1); R = Et, X = ClO4– (2); R = n-Pr, X = NO3– (3); opboR2 = o-phenylenebis(NR-substituted oxamidato); pmdta = N,N,N’,N”,N”-pentamethyldiethylenetriamine). The identities of the heterotrinuclear complexes 1–3 were established by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction studies, which revealed the cationic complex fragments [Cu2Ni(opboR2)(pmdta)2]2+ as not involved in any further intermolecular interactions. As a consequence thereof, the complexes 1–3 possess terminal paramagnetic [Cu(pmdta)]2+ fragments separated by [NiII(opboR2)]2– bridging units representing diamagnetic SNi = 0 states. The magnetic field dependence of the magnetization M(H) of 1–3 at T = 1.8 K has been determined and is shown to be highly reproducible with the Brillouin function for an ideal paramagnetic spin = 1/2 system, verifying experimentally that no magnetic superexchange couplings exists between the terminal paramagnetic [Cu(pmdta)]2+ fragments. Susceptibility measurements versus temperature of 1–3 between 1.8–300 K were performed to reinforce the statement of the absence of magnetic superexchange couplings in these three heterotrinuclear complexes. more...

We have used photoelectron spectroscopy to determine the energy-level alignment at organic heterojunctions made of manganese phthalocyanine (MnPc) and the fullerene C60. We show that this energy-level alignment depends upon the preparation sequence, which is explained by different molecular orientations. Moreover, our results demonstrate that MnPc/C60 interfaces are hardly suited for application in organic photovoltaic devices, since the energy difference of the two lowest unoccupied molecular orbitals (LUMOs) is rather small. more...

We report experimental and theoretical evidence that GaGeTe is a basic Z2 topological semimetal with three types of charge carriers: bulk-originated electrons and holes as well as surface state electrons. This electronic situation is qualitatively similar to the classic 3D topological insulator Bi2Se3, but important differences account for an unprecedented transport scenario in GaGeTe. High-resolution angle-resolved photoemission spectroscopy combined with advanced band structure calculations show a small indirect energy gap caused by a peculiar band inversion at the T-point of the Brillouin zone in GaGeTe. An energy overlap of the valence and conduction bands brings both electron and holelike carriers to the Fermi level, while the momentum gap between the corresponding dispersions remains finite. We argue that peculiarities of the electronic spectrum of GaGeTe have a fundamental importance for the physics of topological matter and may boost the material’s application potential. more...

Electronic topological states of matter exhibit novel types of responses to electromagnetic fields. The response of strong topological insulators, for instance, is characterized by a so-called axion term in the electromagnetic Lagrangian which is ultimately due to the presence of topological surface states. Here we develop the axion Mie theory for the electromagnetic response of spherical particles including arbitrary sources of fields, i.e., charge and current distributions. We derive an axion induced mixing of transverse magnetic and transverse electric modes which are experimentally detectable through small induced rotations of the field vectors. Our results extend upon previous analyses of the problem. Our main focus is on the experimentally relevant problem of electron energy loss spectroscopy in topological insulators, a technique that has so far not yet been used to detect the axion electromagnetic response in these materials. more...

Professional truck drivers frequently face the challenging task of manually backwards manoeuvring articulated vehicles towards the loading bay. Logistics companies experience costs due to damage caused by vehicles performing this manoeuvre. However, driver assistance aimed to support drivers in this special scenario has not yet been clearly established. Additionally, to optimally improve the driving experience and the performance of the assisted drivers, the driver assistance must be able to continuously adapt to the needs and preferences of each driver. This paper presents the VISTA-Sim, a platform that uses a virtual reality (VR) simulator to develop and evaluate personalized driver assistance. This paper provides a comprehensive account of the VISTA-Sim, describing its development and main functionalities. The paper reports the usage of VISTA-Sim through the scenario of parking a semi-trailer truck in a loading bay, demonstrating how to learn from driver behaviours. Promising preliminary results indicate that this platform provides means to automatically learn from a driver’s performance. The evolution of this platform can offer ideal conditions for the development of ADAS systems that can automatically and continuously learn from and adapt to an individual driver. Therefore, future ADAS systems can be better accepted and trusted by drivers. Finally, this paper discusses the future directions concerning the improvement of the platform. more...

We present a ^{125}Te nuclear magnetic resonance (NMR) study in the three-dimensional spin web lattice Cu_{3}TeO_{6} which harbors topological magnons. The ^{125}Te NMR spectra and the Knight-shift K as a function of temperature show a drastic change at T_{S}∼40K much lower than the Néel ordering temperature T_{N}∼61K, providing evidence for the first-order structural phase transition within the magnetically ordered state. Most remarkably, the temperature dependence of the spin-lattice relaxation rate T_{1}^{−1} unravels spin-gap-like magnetic excitations, which sharply sets in at T^{*}∼75K, the temperature well above T_{N}. The spin-gap behavior may be understood by weakly dispersive optical magnon branches of high-energy spin excitations originating from the unique corner-sharing Cu hexagon spin-1/2 network with low coordination number. more...

Despite many efforts to rationalize the strongly correlated electronic ground states in doped Mott insulators, the nature of the doping-induced insulator-to-metal transition is still a subject under intensive investigation. Here, we probe the nanoscale electronic structure of the Mott insulator Sr_{2}IrO_{4−δ} with low-temperature scanning tunneling microscopy and find an enhanced local density of states (LDOS) inside the Mott gap at the location of individual defects which we interpret as defects at apical oxygen sites. A chiral behavior in the topography for those defects has been observed. We also visualize the local enhanced conductance arising from the overlapping of defect states which induces finite LDOS inside of the Mott gap. By combining these findings with the typical spatial extension of isolated defects of about 2 nm, our results indicate that the insulator-to-metal transition in Sr_{2}IrO_{4−δ} could be percolative in nature. more...

Cantilever magnetometry is a measurement technique used to study magnetic nanoparticles. With decreasing sample size, the signal strength is significantly reduced, requiring advances of the technique. Ultrathin and slender cantilevers can address this challenge but lead to increased complexity of detection. We present an approach based on the co-resonant coupling of a micro- and a nanometer-sized cantilever. Via matching of the resonance frequencies of the two subsystems we induce a strong interplay between the oscillations of the two cantilevers, allowing for a detection of interactions between the sensitive nanocantilever and external influences in the amplitude response curve of the microcantilever. In our magnetometry experiment we used an iron-filled carbon nanotube acting simultaneously as nanocantilever and magnetic sample. Measurements revealed an enhancement of the commonly used frequency shift signal by five orders of magnitude compared to conventional cantilever magnetometry experiments with similar nanomagnets. With this experiment we do not only demonstrate the functionality of our sensor design but also its potential for very sensitive magnetometry measurements while maintaining a facile oscillation detection with a conventional microcantilever setup. more...

The reduced dimensionality in two-dimensional materials leads to a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high-resolution microscopy techniques are indispensable. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the two-dimensional material. We demonstrate these features with the example of h-BN, for which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges. more...

In Eu_{2}ZnIrO_{6}, effectively two atoms are active; i.e., Ir is magnetically active, which results in complex magnetic ordering within the Ir sublattice at low temperature. On the other hand, although Eu is a Van Vleck paramagnet, it is active in the electronic channels involving 4f^{6} crystal-field split levels. Phonons, quanta of lattice vibration involving vibration of atoms in the unit cell, are intimately coupled with both magnetic and electronic degrees of freedom (DOF). Here, we report a comprehensive study focusing on the phonons as well as intraconfigurational excitations in double-perovskite Eu_{2}ZnIrO_{6}. Our studies reveal strong coupling of phonons with the underlying magnetic DOF reflected in the renormalization of the phonon self-energy parameters well above the spin-solid phase (T_{N}∼12K) until temperature as high as ∼3T_{N} evidences broken spin rotational symmetry deep into the paramagnetic phase. In particular, all the observed first-order phonon modes show softening of varying degree below ∼3T_{N}, and low-frequency phonons become sharper, while the high-frequency phonons show broadening attributed to the additional available magnetic damping channels. We also observed a large number of high-energy modes, 39 in total, attributed to the electronic transitions between 4f levels of the rare-earth Eu^{3+} ion and these modes shows anomalous temperature evolution as well as mixing of the crystal-field split levels attributed to the strong coupling of electronic and lattice DOF. more...

Recently, several putative quantum spin liquid (QSL) states were discovered in ${\tilde S} = 1/2$ rare-earth based triangular-lattice antiferromagnets (TLAF) with the delafossite structure. A way to clarify the origin of the QSL state in these systems is to identify ways to tune them from the putative QSL state towards long-range magnetic order. Here, we introduce the Ce-based TLAF KCeS$_2$ and show via low-temperature specific heat and $\mu$SR investigations that it yields magnetic order below $T_{\mathrm N} = 0.38$ K despite the same delafossite structure. We identify a well separated ${\tilde S} = 1/2$ ground state for KCeS$_2$ from inelastic neutron scattering and embedded-cluster quantum chemical calculations. Magnetization and electron spin resonance measurements on single crystals indicate a strong easy-plane $g$~factor anisotropy, in agreement with the ab initio calculations. Finally, our specific-heat studies reveal an in-plane anisotropy of the magnetic field-temperature phase diagram which may indicate anisotropic magnetic interactions in KCeS$_2$. more...

The finite coupling between Weyl nodes due to residual disorder is investigated by magnetotransport studies in WTe_{2}. The anisotropic scattering of quasiparticles is evidenced from classical and quantum transport measurements. A theoretical approach using the real band structure is developed in order to calculate the dependence of the scattering anisotropy with the correlation length of the disorder. A comparison between theory and experiments reveals a short correlation length in WTe_{2} (ξ∼5 nm). This result implies a significant coupling between Weyl nodes and other bands. Our study thus shows that a finite intercone scattering rate always exists in weakly disordered type-II Weyl semimetals, such as WTe_{2}, which strongly suppresses topologically nontrivial properties. more...

We report comprehensive Raman-scattering measurements on a single crystal of double-perovskite Nd_{2}ZnIrO_{6} in a temperature range of 4–330 K, spanning a broad spectral range from 20 to 5500cm^{−1}. The paper focuses on lattice vibrations and electronic transitions involving Kramers doublets of the rare-earth Nd^{3+} ion with local C_{1} site symmetry. Temperature evolution of these quasiparticle excitations has allowed us to ascertain the intricate coupling between lattice and electronic degrees of freedom in Nd_{2}ZnIrO_{6}. Strong coupling between phonons and crystal-field excitation is observed via renormalization of the self-energy parameter of the phonons, i.e., peak frequency and linewidth. The phonon frequency shows abrupt hardening and linewidth narrowing below ∼100 K for the majority of the observed first-order phonons. We observed splitting of the lowest Kramers doublets of ground state (^{4}I_{9/2}) multiplets, i.e., lifting of the Kramers degeneracy, prominently at low temperature (below ∼100 K), attributed to the Nd-Nd/Ir exchange interactions and the intricate coupling with the lattice degrees of freedom. The observed splitting is of the order of ∼2–3 meV and is consistent with the estimated value. We also observed a large number of high-energy modes, 46 in total, attributed to the intraconfigurational transitions between 4f^{3} levels of Nd^{3+} coupled to the phonons reflected in their anomalous temperature evolution. more...

The quest for Kitaev spin liquids in particular three-dimensional solids is a long sought goal in condensed matter physics, as these states may give rise to exotic new types of quasiparticle excitations carrying fractional quantum numbers, namely Majorana fermionic excitations. Here we report the experimental signature of this characteristic feature of the Kitaev spin liquid via Raman measurements. Sm_{2}ZnIrO_{6} is a strongly spin-orbit-coupled Mott insulator where J_{eff}=1/2 controls the physics, which provides striking evidence for this characteristic feature of the Kitaev spin liquid. As the temperature is lowered, we find that the spin excitations form a continuum in contrast to the conventional sharp modes expected in ordered antiferromagnets. Our observation of a broad magnetic continuum and anomalous renormalization of the phonon self-energy parameters shows the existence of fractionalization excitations in the double-perovskite structure, as theoretically conjectured in a Kitaev-Heisenberg geometrically frustrated double-perovskite system. more...

Combinations of nontrivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances, material candidates are emerging. Yet, so far a compound that combines a band-inverted electronic structure with an intrinsic net magnetization remains unrealized. MnBi_{2}Te_{4} has been established as the first antiferromagnetic topological insulator and constitutes the progenitor of a modular (Bi_{2}Te_{3})_{n}(MnBi_{2}Te_{4}) series. Here, for n=1, we confirm a nonstoichiometric composition proximate to MnBi_{4}Te_{7}. We establish an antiferromagnetic state below 13 K followed by a state with a net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topologically nontrivial surface state on the MnBi_{4}Te_{7}(0001) surface, analogous to the nonmagnetic parent compound Bi_{2}Te_{3}. Our results establish MnBi_{4}Te_{7} as the first band-inverted compound with intrinsic net magnetization providing a versatile platform for the realization of magnetic topological states of matter. more...

For the first time we present the synthesis of CeO2/Si(O)C core–shell particles prepared by the miniemulsion technique. The Si(O)C core was obtained by means of a polycarbosilane precursor (SMP10), which was subsequently functionalized with ceria and pyrolyzed to the ceramic. The size of these particles could easily be adjusted by varying the surfactants and the surfactant concentration, or by the addition of comonomers. Hence particle sizes ranged from 100 to 1000 nm, tunable by the preparation conditions. All materials were characterized by photon cross correlation spectroscopy, scanning electron microscopy and elemental mapping investigations. Furthermore, first catalytic tests were carried out by temperature programmed oxidation (TPO) of methane, and the activity of this material in lowering the onset temperature of methane combustion by 262 K was documented. more...

In the present paper we discuss the motion of charged particles in three different regions of the Earth magnetotail: in the region with magnetic field reversal and in the vicinities of neutral line of X- and O-types. The presence of small parameters (ratio of characteristic length scales in and perpendicular to the equatorial plane and the smallness of the electric field) allows us to introduce a hierarchy of motions and use methods of perturbation theory. We propose a parameter that plays the role of a measure of mixing in the system. more...

We advance the achievements of Interball-1 and other contemporary missions in exploration of the magnetosheath-cusp interface. Extensive discussion of published results is accompanied by presentation of new data from a case study and a comparison of those data within the broader context of three-year magnetopause (MP) crossings by Interball-1. Multi-spacecraft boundary layer studies reveal that in ∼80% of the cases the interaction of the magnetosheath (MSH) flow with the high latitude MP produces a layer containing strong nonlinear turbulence, called the turbulent boundary layer (TBL). The TBL contains wave trains with flows at approximately the Alfvén speed along field lines and "diamagnetic bubbles" with small magnetic fields inside. A comparison of the multi-point measurements obtained on 29 May 1996 with a global MHD model indicates that three types of populating processes should be operative: large-scale (∼few RE) anti-parallel merging at sites remote from the cusp; medium-scale (few thousandkm) local TBL-merging of fields that are anti-parallel on average; small-scale (few hundredkm) bursty reconnection of fluctuating magnetic fields, representing a continuous mechanism for MSH plasma inflow into the magnetosphere, which could dominate in quasi-steady cases. The lowest frequency (∼1–2mHz) TBL fluctuations are traced throughout the magnetosheath from the post-bow shock region up to the inner magnetopause border. The resonance of these fluctuations with dayside flux tubes might provide an effective correlative link for the entire dayside region of the solar wind interaction with the magnetopause and cusp ionosphere. The TBL disturbances are characterized by kinked, double-sloped wave power spectra and, most probably, three-wave cascading. Both elliptical polarization and nearly Alfvénic phase velocities with characteristic dispersion indicate the kinetic Alfvénic nature of the TBL waves. The three-wave phase coupling could effectively support the self-organization of the TBL plasma by means of coherent resonant-like structures. The estimated characteristic scale of the "resonator" is of the order of the TBL dimension over the cusps. Inverse cascades of kinetic Alfvén waves are proposed for forming the larger scale "organizing" structures, which in turn synchronize all nonlinear cascades within the TBL in a self-consistent manner. This infers a qualitative difference from the traditional approach, wherein the MSH/cusp interaction is regarded as a linear superposition of magnetospheric responses on the solar wind or MSH disturbances. Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers) – Space plasma physics (turbulence; nonlinear phenomena) more...

The magnetic properties of (Y1-xNdx)2BaNiO5 with x = 0.01, 0.02, 0.03, 0.04, and 0.05 are investigated by means of specific heat, magnetic susceptibility, and spectroscopic measurements. We estimate a magnetic contribution of the neodymium subsystem into the magnetic susceptibility and specific heat using temperature dependencies of the splitting of the ground Kramers doublet of the Nd3+ ion obtained from spectroscopic experiments. We estimate also the contribution caused by nickel chain breaks and by ferrons. Different scenarios of low-temperature magnetic behavior are discussed. more...

In the present work we have studied the proximity-induced superconducting triplet pairing in CoOx/Py1/Cu/Py2/Cu/Pb spin-valve structure (where Py = Ni0:81Fe0:19). For CoOx(3 nm)/Py(3 nm)/Cu(4 nm)/Py(0.6 nm)/Cu(2 nm)/Pb(70 nm) we have studied the dependence of the Tc on the angle α between the direction of the cooling field and the external field both applied in the plane of the sample. We obtained that the Tc does not change monotonically with the angle but passes through a minimum. To observe an “isolated” triplet spin-valve effect we exploited the oscillatory feature of the magnitude of the ordinary spin-valve effect ΔTc in the dependence of the Py2-layer thickness dPy2. We determined the value of dPy2 at which ΔTc caused by the ordinary spin-valve effect is suppressed. This means that the difference in the Tc between the antiparallel and parallel mutual orientation of magnetizations of the Py1 and Py2 layers is zero. For such a sample a “pure” triplet spin-valve effect which causes the minimum in Tc at the orthogonal configuration of magnetizations has been observed. more...