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Tomonaga-Luttinger liquid behavior has been observed within 1D defects in transition metal dichalcogenides. Here, using complementary experiments and engineered defects, the authors demonstrate the importance of graphene as a substrate and its role in the formation of this quasiparticle excitation in 2D WS₂.

In frustrated magnets geometric constraints are expected to prevent any magnetic ordering. In this work, normally non-magnetic atoms on a silicon surface display an ordered state despite geometric frustration. This offers new ways of controlling magnetism on surfaces.

Synthesis of heterostructures of magnetic intercalation compounds in transition metal dichalcogenides (TMDs) via directed topotactic reactions enables the creation of multi-component magnetic architectures, overcoming limitations of crystallographic incommensurability

Chromium sulfur bromide is an air-stable van der Waals magnet, which has a large optical response. Here, Smolenski et al find a large exciton binding energy CrSBr, which they attribute to localization due to the quasi one-dimensional electronic bands.

Angle-resolved photoemission spectroscopy of superconducting magic-angle twisted bilayer graphene reveals flat-band replicas that are indicative of strong electron–phonon coupling; these replicas are absent in non-superconducting twisted bilayer graphene.

Experiments that directly probe the quantum geometric tensor in solids have not been reported. Now, the quantum metric and spin Berry curvature—dual components of the quantum geometric tensor—have been simultaneously measured in reciprocal space.

Electronic rotons and Wigner crystallites have been observed experimentally and numerically in a two-dimensional dipole liquid.

Ca₂RuO₄ is a Mott insulator that becomes a metal when a current is passed through it. Now, the changes in its electronic structure are revealed as this transition takes place.

Analysis of the antiferromagnetic ordered phase of kagome lattice FeGe suggests that charge density wave is the result of a combination of electronic-correlations-driven antiferromagnetic order and instability driven by van Hove singularities.

The identification of dark states—quantum states that do not interact with photons—in real materials may help to address many unsolved issues in condensed-matter physics. Now, they have been identified in palladium diselenide.

Topological insulators have a conducting surface on which spin currents are not easily scattered, although the addition of magnetic impurities does affect electronic behaviour. But is this situation unique? Graphene comes to mind.

The flat electronic bands that are associated with ordered phases in twisted bilayer graphene at a magic twist angle have been imaged using angle-resolved photoemission spectroscopy.

Point defects in 2D semiconductors have potential for quantum computing applications, but their controlled design and synthesis remains challenging. Here, the authors identify and fabricate a promising quantum defect in 2D WS₂ via high-throughput computational screening and scanning tunnelling microscopy.

Here, the authors report the observation of an interlayer plasmon polaron in heterostructures composed of graphene and monolayer WS₂. This is manifested in the ARPES spectra as a strong quasiparticle peak accompanied by several carrier density-dependent shake-off replicas around the WS₂ conduction band minimum.

A microfocused angle-resolved photoemission spectroscopy study of single layers of WS₂ on hexagonal boron nitride reveals that, upon electron doping, trionic interactions cause a giant increase of the spin splitting in the valence band.

The authors develop a high-spatial-resolution photoemission technique to show variation of the energy of the Dirac point of approximately 50 meV. They also find an interplay between bulk and surface states.

Topological states in atomically thin quantum spin Hall insulators suffer from instability against environmental factors. Here, the authors devise a strategy to preserve topologically protected states in monolayer indenene through graphene intercalation.

Thermal annealing of SiC produces graphene layers on an insulating substrate, but the material is highly inhomogeneous. It is now shown that an argon atmosphere during annealing improves uniformity of the graphene layers dramatically and yields better transport characteristics. This is a very important result for the development of graphene-based electronic devices.

As indicated by direct band-structure measurements and calculations, tiny native imperfections in bilayer graphene are sufficient to cause the generation of coexisting massive and massless Dirac fermions. The massless spectrum is robust against strong electric fields and has a closed-arc topology consisting of a unique chiral pseudospin texture.

A study shows that in electron-doped Ba(Fe_1−xCo_x)₂As₂, the presence or absence of superconductivity and antiferromagnetism can be linked directly to changes in the Fermi surface—as measured by angle-resolved photoemission spectroscopy.

The quasi-one-dimensional bismuth iodide β-Bi₄I₄ is theoretically predicted and experimentally confirmed to exhibit a (1;110) Z₂ strong topological insulator phase.

The rotation of polarized light in certain materials when subject to a magnetic field is known as the Faraday effect. Remarkably, just one atomic layer of graphene exhibits Faraday rotations that would only be measurable in other materials many hundreds of micrometres thick.

Using valley-resolved scanning tunnelling spectroscopy, twisted WSe₂ bilayers are studied, including incommensurate dodecagon quasicrystals at 30° and commensurate moiré crystals at 21.8° and 38.2°.

Electrons in f orbitals can create localized states that interact strongly and drive strange metal and critical behaviour via the Kondo mechanism. Now a mechanism of geometric frustration enables similar phenomena with d electrons.

Angle-resolved photoemission spectroscopy of CaNi₂ shows a band with vanishing dispersion across the full 3D Brillouin zone that is identified with the pyrochlore flat band as well as two additional flat bands that arise from multi-orbital interference of Ni d-electrons.

The presence of excitonic instability and its relationship with a structural transition in Ta₂NiSe₅ has been debated. Chen et al. map out the electronic bands and lattice distortion across the semimetal-to-semiconductor transition with sulfur doping, revealing the crucial role of electron-phonon coupling.

The tunability of electronic properties is a central goal of research into topological semimetals. Here, the authors report Weyl nodal ring states in the magnetic semimetal EuGa₄ and link the nodal ring state to the observed large non-saturating magnetoresistance.

The observation of band structure features typical of the kagome lattice in FeGe suggests that an interplay of magnetism and electronic correlations determines the physics of this material.

Films of the correlated oxide NdNiO₃ form a metallic antiferromagnetic phase that can be identified using electrical currents, raising the prospect of applications in spintronics.

A prototypical kagome metal with magnetic and topological properties is identified.

The authors use high-resolution angle-resolved photoemission spectroscopy to determine the microscopic structure of three-dimensional charge order in AV₃Sb₅ (A = K, Rb, Cs) and its interplay with superconductivity.

The physics of Mott insulators is obscured by the interplay between competing orders and fluctuations. Here, the authors track the evolution of the electronic structure of Mott insulator strontium iridate as the iridium atoms are replaced by rhodium, providing insight into this exotic state of matter.

Spectroscopic measurements show how the features of the band structure related to the kagome lattice in CsV₃Sb₅ contribute to the observed strongly correlated phases.

The experimental realization of lattice-born flat bands with nontrivial topology has been elusive. Here, the authors observe topological flat bands near the Fermi level in a kagome metal CoSn, with flat bands as well as Dirac bands originating from 3d orbitals in a frustrated kagome geometry.

A back-bending band structure and an emerging pseudogap are observed at the interface between a crystalline solid (black phosphorus) and disordered alkali-metal dopants.

Single-crystal 2D metals are stabilized at the interface between epitaxial graphene and silicon carbide, with strong internal gradients in bonding character. The confined 2D metals demonstrate compelling superconducting properties.

Exciton condensation may emerge at room temperature in topological materials with strong Coulomb interactions and vanishing electron effective mass. Here, Hou et al. report the formation of excitons in Bi_2-xSb_xSe₃ nanoribbons, which can transport over hundreds of micrometres before recombination up to 40 K, further implying exciton condensation.

Anisotropic honeycomb crystal of black phosphorous is found to have pseudospin polarization greater than 95% at room temperature, attributed to the merging of Dirac cones. This bipolar pseudospin semiconductor may be useful for pseudospintronics.

Fe₃Sn₂ hosts massive Dirac fermions, owing to the underlying symmetry properties of the bilayer kagome lattice in the ferromagnetic state and the atomic spin–orbit coupling.

Gaussian process regression (GPR) is a powerful, non-parametric and robust technique for uncertainty quantification and function approximation that can be applied to optimal and autonomous data acquisition. This Review introduces the basics of GPR and discusses several use cases from different fields.

Doping is a tried and tested method to tune the properties of a range of quantum materials either by introducing defects into the system or engineering the charge carrier concentration. Here, the authors use photoemission spectroscopy to investigate the effects of surface doping of alkali metals on the Mott insulator Ca₂RuO₄, revealing an orbital-selective surface metal-insulator transition induced by the surface-dopant interaction.