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Abstract Altermagnets are a novel class of magnetic materials, where magnetic order is staggered both in coordinate and momentum space. The metallic rutile oxide RuO2, long believed to be a textbook Pauli paramagnet, recently emerged as a putative workhorse altermagnet when resonant X-ray and neutron scattering studies reported nonzero magnetic moments and long-range collinear order. While some experiments seem consistent with altermagnetism, magnetic order in RuO2 remains controversial. We show that RuO2 is nonmagnetic, both in bulk and thin film. Muon spectroscopy complemented by density-functional theory finds at most 1.14 × 10−4 μ B/Ru in bulk and at most 7.5 × 10−4 μ B/Ru in 11 nm epitaxial films, at our spectrometers’ detection limit, and dramatically smaller than previously reported neutron results that were used to rationalize altermagnetic behavior. Our own neutron diffraction measurements on RuO2 single crystals identify multiple scattering as the source for the false signal in earlier studies.

Abstract Individual optical addressing in chains of trapped atomic ions requires the generation of many small, closely spaced beams with low cross-talk. Furthermore, implementing parallel operations necessitates phase, frequency, and amplitude control of each individual beam. Here, we present a scalable method for achieving all of these capabilities using a high-performance integrated photonic chip coupled to a network of optical fibre components. The chip design results in very low cross-talk between neighbouring channels even at the micrometre-scale spacing by implementing a very high refractive index contrast between the channel core and cladding. Furthermore, the photonic chip manufacturing procedure is highly flexible, allowing for the creation of devices with an arbitrary number of channels as well as non-uniform channel spacing at the chip output. We present the system used to integrate the chip within our ion trap apparatus and characterise the performance of the full individual addressing setup using a single trapped ion as a light-field sensor. Our measurements showed intensity cross-talk below ~10–3 across the chip, with minimum observed cross-talk as low as ~10–5.

The trend towards equipping buildings with active space cooling technology is expected to continue, due to the warming climate. In addition, the electrification of mobility and industry, and the massive rollout of photovoltaics, may put Austria’s power grids under stress if adequate mechanisms are not implemented in time. This study investigates the magnitudes of the loads induced by this increasing demand for cooling, together with the relief that passive cooling measures can provide. Data from current climate models, measured real load profiles from households, building stock models, and dynamic building simulations are utilised, alongside stakeholder and expert opinions, to fine-tune the analysis. This article suggests plausible scenarios for the development of the demand for cooling energy in Austria until 2050, and analyses the aggregated effect of the different options for cooling on the electricity power grid. The integration of cooling loads is expected to cause overloads or voltage violations only for a few types of grid within the periods investigated here. Subsidy programs in the building sector often do not properly consider cooling demand. Building regulations and subsidies should therefore focus on passive measures, and only when these are not sufficient should measures related to active cooling be implemented.

Abstract Organoid and spheroid technology provide valuable insights into developmental biology and oncology. Optical coherence tomography (OCT) is a label-free technique that has emerged as an excellent tool for monitoring the structure and function of these samples. However, mature organoids are often too opaque for OCT. Access to multi-angle views is highly desirable to overcome this limitation, preferably with non-contact sample handling. To fulfil these requirements, we present an ultrasound-induced reorientation method for multi-angle-OCT, which employs a 3D-printed acoustic trap inserted into an OCT imaging system, to levitate and reorient zebrafish larvae and tumor spheroids in a controlled and reproducible manner. A model-based algorithm was developed for the physically consistent fusion of multi-angle data from a priori unknown angles. We demonstrate enhanced penetration depth in the joint 3D-recovery of reflectivity, attenuation, refractive index, and position registration for zebrafish larvae, creating an enabling tool for future applications in volumetric imaging.

Abstract Atomic monolayers on semiconductor surfaces represent an emerging class of functional quantum materials in the two-dimensional limit — ranging from superconductors and Mott insulators to ferroelectrics and quantum spin Hall insulators. Indenene, a triangular monolayer of indium with a gap of ~ 120 meV is a quantum spin Hall insulator whose micron-scale epitaxial growth on SiC(0001) makes it technologically relevant. However, its suitability for room-temperature spintronics is challenged by the instability of its topological character in air. It is imperative to develop a strategy to protect the topological nature of indenene during ex situ processing and device fabrication. Here we show that intercalation of indenene into epitaxial graphene provides effective protection from the oxidising environment, while preserving an intact topological character. Our approach opens a rich realm of ex situ experimental opportunities, priming monolayer quantum spin Hall insulators for realistic device fabrication and access to topologically protected edge channels.

Abstract Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.

Minimally invasive surgeries call for surgical tools that can work at the mesoscale. Here, Gu et al. present a class of magnetic soft robotic chains that can self fold into large assemblies with stable configurations using a combination of elastic and magnetic energies stored in printed chain material.

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.

A new technology enables fast production of waveguide (SPIM-WG) based high performance optical devices with very low loss, precisely organized refractive index, arbitrarily variable cross-sections and high coupling efficiency.

In the life sciences, there has been growing awareness that the traditional 2D cell culture model has its limitations in advancing our understanding of the mechanisms that underlie cell behavior, as the behavior and response of cells depend on the 3D microenvironment. Studying models such as suspended cell clusters and organoids is a step toward closing the gap between in vitro and in vivo studies. The fact that sample confinement and contact with surfaces have an impact on cells creates a need for contact-less tools for the inspection of live biological samples. Recently, we developed an acoustofluidic chip to trap and manipulate sub-millimeter-sized biological samples, and here, we demonstrate that this device can be adapted to support high-resolution imaging and illumination scanning for multi-view image acquisition. After coupling acoustic bulk waves into a microfluidic chip, the sample is levitated by an optically transparent transducer in the vertical direction. Two orthogonal side-transducers give additional control over the sample. By tuning the relative strengths of the three transducers and thus inducing an acoustic torque, we can transiently rotate the sample into various orientations for image acquisition. Under different operating conditions, exciting other modes, we can also induce sustained rotation of samples by means of other torque contributions and around axes perpendicular to the imaging axis, which is important to avoid “missing cone” artifacts in the tomographic reconstruction of the sample. We will discuss the modifications to our previously established device that were necessary to comply with the requirements for high-NA imaging and high-NA illumination. We provide a characterization of the performance and show examples of rotation and reorientation of biological samples, such as large pollen grains and cancer spheroids.

Most existing urban district heating networks (DHNs) operate on relatively high temperatures. Typically, resulting from 2nd and 3rd generation of district heating (DH), 90–130 °C is used as supply and 50–70 °C as return temperature. On the contrary, low temperature district heating networks (LTDHN) with supply temperatures between 30 °C and 70 °C allow a more efficient operation of the network and can further utilize renewable heat sources such as solar or geothermal energy, low temperature waste heat, or even ambient heat. However, high temperature DHNs cannot easily be modified and transformed into LTDHNs due to established operating conditions and assets. Therefore, the integration of a low-temperature sub-network (sub-LTDHN) and creating an energy cascade is an opportunity to increase the efficiency and sustainability of the overall network. The sub-LTDHN is integrated into the return line of the superior DHN, hence leading to a reduction of the return temperature of the superior DHN. Sub-LTDHNs can be a key enabler for the decarbonization of urban DHNs by enabling an efficient utilization of local energy sources and have the potential to reduce substantially the overall network temperatures. At the same time, a high temperature backup from the main network to the sub-LTDHN is available.Within this study, theoretical conceptualized as well as practical examples of sub-LTDHN are compiled using literature research, expert interviews and the professional international network to DHN operators. Despite the potential advantages of sub-LTDHNs, there are several technical, legislative and economic issues related to their implementation, which is the reason why they are hardly implemented. The review investigates the revealed solutions and conditions of the compiled sub-LTDHNs and tries to generalize them in order to allow its replicability. Therefore, general results on implementations, frameworks, barriers and enablers are derived (“lessons learnt”) and good practices are properly elaborated.

Atomic monolayers of large-gap quantum spin Hall insulators are challenging to synthesize. Here, the authors realize massive Dirac fermions emerging from Bloch wave-function interference on a triangular lattice and achieve topologically non-trivial domains with unprecedented spatial extension.

Angle-resolved photoemission spectroscopy (ARPES) is a method that measures orbital and band structure contrast through the momentum distribution of photoelectrons. Its simplest interpretation is obtained in the plane-wave approximation, according to which photoelectrons propagate freely to the detector. The photoelectron momentum distribution is then essentially given by the Fourier transform of the real-space orbital. While the plane-wave approximation is remarkably successful in describing the momentum distributions of aromatic compounds, it generally fails to capture kinetic-energy-dependent final-state interference and dichroism effects. Focusing our present study on quasi-freestanding monolayer graphene as the archetypical two-dimensional (2D) material, we observe an exemplary E_{kin}-dependent modulation of, and a redistribution of spectral weight within, its characteristic horseshoe signature around the K[over ¯] and K[over ¯]^{′} points: both effects indeed cannot be rationalized by the plane-wave final state. Our data are, however, in remarkable agreement with ab initio time-dependent density functional simulations of a freestanding graphene layer and can be explained by a simple extension of the plane-wave final state, permitting the two dipole-allowed partial waves emitted from the C 2p_{z} orbitals to scatter in the potential of their immediate surroundings. Exploiting the absolute photon flux calibration of the Metrology Light Source, this scattered-wave approximation allows us to extract E_{kin}-dependent amplitudes and phases of both partial waves directly from photoemission data. The scattered-wave approximation thus represents a powerful yet intuitive refinement of the plane-wave final state in photoemission of 2D materials and beyond.

In analogy to electricity transmission networks, this paper analyzes the concept of supra-regional district heating networks (SR-DHN), connecting a large number of actors. Using a back-casting approach, a SR-DHN is assumed to exist and thus, implementation challenges, such as economic feasibility and energy losses, are circumvented in the first step (but are analyzed in the discourse). The paper then analyzes, in an interdisciplinary qualitative manner and supported by a case study, what technical, operational, economic and legal issues must have been resolved. Results show that the heat transmission network, being the backbone of the SR-DHN, is an expensive infrastructure, but is likely to become economic in a non-fossil energy system. By decreasing the reliance on single waste heat sources, SR-DHN allows longer payback periods and can thus be an enabler for using industrial waste heat. However, involving many actors requires comprehensive contractual foundations. The derived hypothesis is that SR-DHN, which is predominantly fed by waste heat, shall be operated with lower temperatures in winter (feeding the return while minimizing expensive winter losses) and high temperatures in summer (enabling alternative usages while accepting high but inexpensive summer losses).

Despite large amounts of available roof space, long pay-back periods for investments in photovoltaic (PV) power plants often hinder PV installations in industrial parks. Photovoltaic citizen participation initiatives (PV-CPI) are an alternative way of financing PV power plants that add non-financial benefits to these investments. This paper analyzed the feasibility of the installation of PV power plants focused on high rates of self-consumption financed by citizen participation initiatives on the roofs of five companies located in the Austrian Ennshafen industrial business park based on the net present value and the discounted pay-back period and compared it to a standard financing scheme, assuming a predetermined interest rate for participants as well as economies of scale with respect to the specific installation costs due to a joint purchase of the PV power plants. To calculate the feasibility, site-specific data and literature input have been used. The results show that despite an interest rate above the current interest rates of conservative forms of investments provided to (small-scale) investors, a payback-period of 17–23 years can be reached while the joint purchase can lead to a competitive feasibility of the PV-CPI compared to an individual purchase of PV power plants.

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.

Belted cattle have a circular belt of unpigmented hair and skin around their midsection. The belt is inherited as a monogenic autosomal dominant trait. We mapped the causative variant to a 37 kb segment on bovine chromosome 3. Whole genome sequence data of 2 belted and 130 control cattle yielded only one private genetic variant in the critical interval in the two belted animals. The belt-associated variant was a copy number variant (CNV) involving the quadruplication of a 6 kb non-coding sequence located approximately 16 kb upstream of the TWIST2 gene. Increased copy numbers at this CNV were strongly associated with the belt phenotype in a cohort of 333 cases and 1322 controls. We hypothesized that the CNV causes aberrant expression of TWIST2 during neural crest development, which might negatively affect melanoblasts. Functional studies showed that ectopic expression of bovine TWIST2 in neural crest in transgenic zebrafish led to a decrease in melanocyte numbers. Our results thus implicate an unsuspected involvement of TWIST2 in regulating pigmentation and reveal a non-coding CNV underlying a captivating Mendelian character.