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Topological semimetals in crystals with a chiral structure (which possess a handedness due to a lack of mirror and inversion symmetries) are expected to display numerous exotic physical phenomena, including fermionic excitations with large topological charge1, long Fermi arc surface states2,3, unusual magnetotransport4 and lattice dynamics5, as well as a quantized response to circularly polarized light6. So far, all experimentally confirmed topological semimetals exist in crystals that contain mirror operations, meaning that these properties do not appear. Here, we show that AlPt is a structurally chiral topological semimetal that hosts new four-fold and six-fold fermions, which can be viewed as a higher spin generalization of Weyl fermions without equivalence in elementary particle physics. These multifold fermions are located at high symmetry points and have Chern numbers larger than those in Weyl semimetals, thus resulting in multiple Fermi arcs that span the full diagonal of the surface Brillouin zone. By imaging these long Fermi arcs, we experimentally determine the magnitude and sign of their Chern number, allowing us to relate their dispersion to the handedness of their host crystal.AlPt is shown to be a chiral topological material with four-fold and six-fold degeneracies in the band structure. Fermi arc edge states span the whole Brillouin zone and their dispersion enables identification of the handedness of the chiral material.

It has recently been proposed that combining chirality with topological band theory results in a totally new class of fermions. Understanding how these unconventional quasiparticles propagate and interact remains largely unexplored so far. Here, we use scanning tunneling microscopy to visualize the electronic properties of the prototypical chiral topological semimetal PdGa. We reveal chiral quantum interference patterns of opposite spiraling directions for the two PdGa enantiomers, a direct manifestation of the change of sign of their Chern number. Additionally, we demonstrate that PdGa remains topologically non-trivial over a large energy range, experimentally detecting Fermi arcs in an energy window of more than 1.6 eV that is symmetrically centered around the Fermi level. These results are a consequence of the deep connection between chirality in real and reciprocal space in this class of materials, and, thereby, establish PdGa as an ideal topological chiral semimetal. Direct visualization of chiral effects in topological chiral semimetals remains elusive. Here, Sessi et al . demonstrate that quasiparticle scattering at impurities in the two enantiomers of PdGa gives rise to handedness dependent quantum interference patterns.

In atomically thin transition metal dichalcogenide semiconductors, there is a crossover from indirect to direct band gap as the thickness drops to one monolayer, which comes with a fast increase of the photoluminescence signal. Here, we show that for different alloy compositions of WS 2(1− x ) Se 2 x this trend may be significantly affected by the alloy content and we demonstrate that the sample with the highest Se ratio presents a strongly reduced effect. The highest micro-PL intensity is found for bilayer WS 2(1− x ) Se 2 x ( x  = 0.8) with a decrease of its maximum value by only a factor of 2 when passing from mono-layer to bi-layer. To better understand this factor and explore the layer-dependent band structure evolution of WS 2(1− x ) Se 2 x , we performed a nano-angle-resolved photoemission spectroscopy study coupled with first-principles calculations. We find that the high micro-PL value for bilayer WS 2(1− x ) Se 2 x ( x  = 0.8) is due to the overlay of direct and indirect optical transitions. This peculiar high PL intensity in WS 2(1− x ) Se 2 x opens the way for spectrally tunable light-emitting devices.

Twisted van der Waals heterostructures have recently been proposed as a condensed-matter platform for realizing controllable quantum models due to the low-energy moiré bands with specific charge distributions moiré superlattices. Here, combining angle-resolved photoemission spectroscopy with submicron spatial resolution (μ-ARPES) and scanning tunneling microscopy (STM), we performed a systematic investigation on the electronic structure of 5.1° twisted bilayerWSe2that hosts correlated insulating and zero-resistance states. Interestingly, contrary to one’s expectation, moiré bands were observed only atΓvalley but notKvalley inμ-ARPES measurements, and correspondingly, our STM measurements clearly identified the real-space honeycomb- and kagome-shaped charge distributions at the moiré length scale associated with theΓ-valley moiré bands. These results not only reveal the unusual valley-dependent moiré-modified electronic structure in twisted transition metal dichalcogenides, but also highlight theΓ-valley moiré bands as a promising platform for exploring strongly correlated physics in emergent honeycomb and kagome lattices at different energy scales.

Pressure represents a clean tuning parameter for traversing the complex phase diagrams of interacting electron systems, and as such has proved of key importance in the study of quantum materials. Application of controlled uniaxial pressure has recently been shown to more than double the transition temperature of the unconventional superconductor Sr2RuO4, leading to a pronounced peak in Tc versus strain whose origin is still under active debate. Here we develop a simple and compact method to passively apply large uniaxial pressures in restricted sample environments, and utilise this to study the evolution of the electronic structure of Sr2RuO4 using angle-resolved photoemission. We directly visualise how uniaxial stress drives a Lifshitz transition of the γ-band Fermi surface, pointing to the key role of strain-tuning its associated van Hove singularity to the Fermi level in mediating the peak in Tc. Our measurements provide stringent constraints for theoretical models of the strain-tuned electronic structure evolution of Sr2RuO4. More generally, our experimental approach opens the door to future studies of strain-tuned phase transitions not only using photoemission but also other experimental techniques where large pressure cells or piezoelectric-based devices may be difficult to implement.

Waste from the forestry industry, particularly from logging and wood processing operations, constitutes a significant portion of the harvested timber. The issue of road surface stability on weak bearing soils is one of the most pressing challenges in modern road construction. Weak soils, such as peatlands, loams, and clay soils, have low bearing capacity and are prone to substantial deformations under load. The aim of this article is to assess the feasibility of using wood processing waste to reinforce soils on logging roads. Winter logging roads are a crucial element of transport infrastructure, ensuring efficient delivery of timber and other forest resources. However, under positive temperatures and heavy loads, such roads are susceptible to destruction and deformation. Moreover, this type of road is temporary and deteriorates during the spring season. One promising direction in strengthening road surfaces is the use of loose forest materials such as wood chips and sawdust. This article examines the mechanisms of action of these materials, their advantages and disadvantages, as well as examples of successful applications.

Twisted bilayer graphene (tBLG) provides a fascinating platform for engineering flat bands and inducing correlated phenomena. By designing the stacking architecture of graphene layers, twisted multilayer graphene can exhibit different symmetries with rich tunability. For example, in twisted monolayer-bilayer graphene (tMBG) which breaks the C 2 z symmetry, transport measurements reveal an asymmetric phase diagram under an out-of-plane electric field, exhibiting correlated insulating state and ferromagnetic state respectively when reversing the field direction. Revealing how the electronic structure evolves with electric field is critical for providing a better understanding of such asymmetric field-tunable properties. Here we report the experimental observation of field-tunable dichotomic electronic structure of tMBG by nanospot angle-resolved photoemission spectroscopy (NanoARPES) with operando gating. Interestingly, selective enhancement of the relative spectral weight contributions from monolayer and bilayer graphene is observed when switching the polarity of the bias voltage. Combining experimental results with theoretical calculations, the origin of such field-tunable electronic structure, resembling either tBLG or twisted double-bilayer graphene (tDBG), is attributed to the selectively enhanced contribution from different stacking graphene layers with a strong electron-hole asymmetry. Our work provides electronic structure insights for understanding the rich field-tunable physics of tMBG. The phase diagram of twisted monolayer-bilayer graphene depends on the electric field direction, exhibiting phases similar to twisted bilayer and double-bilayer graphene. Here the authors study the field dependent electronic structure, in particular flat bands, using nano-ARPES and explain the field-tunability.

Control of atomic-scale interfaces between materials with distinct electronic structures is crucial for the design and fabrication of most electronic devices. In the case of two-dimensional materials, disparate electronic structures can be realized even within a single uniform sheet, merely by locally applying different vertical gate voltages. Here, we utilize the inherently nano-structured single layer and bilayer graphene on silicon carbide to investigate lateral electronic structure variations in an adjacent single layer of tungsten disulfide (WS 2 ). The electronic band alignments are mapped in energy and momentum space using angle-resolved photoemission with a spatial resolution on the order of 500 nm (nanoARPES). We find that the WS 2 band offsets track the work function of the underlying single layer and bilayer graphene, and we relate such changes to observed lateral patterns of exciton and trion luminescence from WS 2 . Sharp atomic interfaces between materials dictate the interface’s electronic properties. The authors use angle-resolved photoemission spectroscopy with a spatial resolution of ~500 nm to investigate the nanoscale electronic band structure and band alignment in a lateral heterostructure composed of WS 2 placed on alternating nano-stripes of monolayer and bilayer graphene.

Type-II iron-based superconductors (Fe-SCs), the alkali-metal-intercalated iron selenide A x Fe 2− y Se 2 (A = K, Tl, Rb, etc.) with a superconducting transition temperature of 32 K, exhibit unique properties such as high Néel temperature, Fe-vacancies ordering, antiferromagnetically ordered insulating state in the phase diagram, and mesoscopic phase separation in the superconducting materials. In particular, the electronic and structural phase separation in these systems has attracted intensive attention since it provides a platform to unveil the insulating parent phase of type-II Fe-SCs that mimics the Mott parent phase in cuprates. In this work, we use spatial- and angle-resolved photoemission spectroscopy to study the electronic structure of superconducting K x Fe 2− y Se 2 . We observe clear electronic phase separation of K x Fe 2− y Se 2 into metallic islands and insulating matrix, showing different K and Fe concentrations. While the metallic islands show strongly dispersive bands near the Fermi level, the insulating phase shows an energy gap up to 700 meV and a nearly flat band around 700 meV below the Fermi energy, consistent with previous experimental and theoretical results on the superconducting K 1− x Fe 2 Se 2 (122 phase) and Fe-vacancy ordered K 0.8 Fe 1.6 Se 2 (245 phase), respectively. Our results not only provide important insights into the mysterious composition of phase-separated superconducting and insulating phases of K x Fe 2− y Se 2 , but also present their intrinsic electronic structures, which will shed light on the comprehension of the unique physics in type-II Fe-SCs.

The paper presents the results of scientific research of certain features of wood resources processing at the enterprises of the forest industry. Considering that the forest industry is actively developing, the volumes of processed raw materials are increasing, the amount of generated secondary wood resources (waste) is increasing. The purpose of the work is to identify some key features of their use. For this purpose, the analysis of literary sources was used. Practical experience of domestic and foreign timber companies was also considered. As a result, a significant lag of the Russian timber industry from foreign best practices was revealed. In particular, the volume of manufactured products is significantly inferior to those of timber reserves and processed raw materials. This is due to the low share of participation and efficiency in the utilization of secondary wood resources. Another important conclusion was that the main problem in terms of the secondary wood resources utilization is to find optimal ways of using secondary wood raw materials. Significant volumes of wood waste generation in various technological processes were shown. Separate requirements were revealed and demonstrated to the initial raw materials to obtain products from the raw materials of wood. An important outcome was that the higher feedstock requirements of large-scale production facilities were identified. Smaller production facilities are often more flexible and adaptable to the available resources.