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Bistable superlattice switching between two lattice configurations with sharply contrasting periodicities has been observed in monolayer TaIrTe₄, a dual quantum spin Hall insulator.

Using a tuning fork-based probe, the authors offer evidence of 2D magnetic moment along the c-axis of CsV₃Sb₅. Their findings suggest that loop currents within the kagome lattice can generate orbital magnetism.

The control of different types of magnetic order is central to the study and development of spintronic devices. Here, the authors evidence an exchange-stabilized helix state with a low energy barrier for reversal in a room-temperature antiferromagnetic Heusler material.

Heusler compounds have been predicted to host topological order with other emergent properties, which yet awaits for experimental evidence. Here, Liu et al. report a direct observation of topological surface states on half-Heusler compounds LnPtBi.

A special class of topological Weyl semimetal state is predicted without respecting Lorentz symmetry. Here, Jianget al. report direct visualization of the unique surface Fermi arcs of MoTe₂, confirming its type-II topological Weyl semimetal nature.

Spintronics requires materials in which most of the spins at the Fermi edge are aligned with each other at room temperatures. Jourdan et al. observe such a spin polarization of 93% in Co₂MnSi—a Heusler alloy amenable to many spintronic applications; evidence of the material’s half-metallicity.

Surface Fermi arcs (SFAs) are characteristic features of a topological Weyl semimetal but there is no easy way to manipulate them so far. Here, the authors report manipulation of the shape, size and connections of SFAs in a Weyl semimetal NbAs, leading to an unusual topological Lifshitz transition.

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.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are emerging candidates for organic 2D crystal materials, but the precise implantation of chirality has yet to be demonstrated. Here, the authors report a side chain-induced chirality amplification strategy to achieve tunable chiral expression in 2D c-MOFs.

The mechanism of the multiple-q charge density wave phase in the antiferromagnetic kagome metal FeGe is not fully understood. Here the authors reveal dimerization-driven hexagonal charge-diffuse precursor and identify the fraction of dimerized/undimerized states as the key order parameter of the phase transition.

Experimental evidence of coherent charge transport in the normal state of the kagome metal CsV₃Sb₅ is presented, revealing the nature of correlated order in kagome metals and new directions for exploring quantum coherence in correlated electron systems.

Chiral topological materials have been predicted to host orbital angular momentum monopoles, which can be useful for orbitronics applications. Now such monopoles have been imaged in chiral materials.

Superconductivity was recently observed in the binary iron-based compound, FeSe. It is now shown that under pressure, the transition temperature can rise above 36 K. In addition, no static magnetic ordering is observed for this system, contrary to FeAs superconductors.

Distinguishing band and Mott insulators experimentally represents a longstanding challenge. Here, the authors demonstrate a momentum-resolved signature of a dimerized Mott-insulator in the out-of-plane spectral function of Nb₃Br₈.

The dynamical axion quasiparticle, which is directly analogous to the hypothetical fundamental axion particle, is observed in two-dimensional MnBi₂Te₄, and has implications for quantum chromodynamics, cosmology and string theory.

Electrical transport measurements reveal that Co₃Sn₂S₂ is probably a magnetic Weyl semimetal, and hosts the highest simultaneous anomalous Hall conductivity and anomalous Hall angle. This is driven by the strong Berry curvature near the Weyl points.

Spin-momentum locking is a fundamental property of condensed matter systems. Here, the authors evidence parallel Weyl spin-momentum locking of multifold fermions in the chiral topological semimetal PtGa.

Topological semimetals with space-inversion and time-reversal symmetry breaking have attracted attention recently. Here, using a combination of experimental techniques and calculations, the authors demonstrate the tunability of the Weyl nodes via magnetism and pressure in the ferromagnetic Weyl semimetal CeAlSi.

A new type of Hall effect—the layer Hall effect—is produced in a 2D antiferromagnet that does not exhibit any net magnetization.

The recently discovered charge density wave in ScV₆Sn₆ kagome metal is under intense debate. By using a combination of experimental and theoretical techniques, the authors point to the role of flat phonon mode softening and momentum-dependent electron-phonon coupling in the formation of the charge density wave.

L. Rocchino et al. experimentally demonstrate a magnetic field effect transistor based on the Weyl semimetal NbP as the active channel material. A gate magnetic field is generated by current flowing in an integrated superconductor NbN. The device operation relies on the extreme magnetoresistance of the NbP.

Experiments show that TaAs is a three-dimensional topological Weyl semimetal.

Band structures with Fermi arcs characteristic of Weyl semimetals are observed on NbP and TaP. By studying NbP, TaP and TaAs, the evolution of the Fermi surface with the spin–orbit coupling is reported.

Heusler alloy thin films with a distorted tetragonal structure have potential spintronics applications given their bulk perpendicular magnetic anisotropy. Here, the authors demonstrate large perpendicular magnetic anisotropy in Mn₃Ge thin films accompanied by negative tunnelling magnetoresistance.

In the charge-density-wave Weyl semimetal (TaSe₄)₂I, an axion is observed and identified as a sliding mode in the charge-density-wave phase characterized by anomalous magnetoelectric transport effects.

The ultra-quantum limit refers to the high magnetic-field regime where electrons are confined to the lowest Landau level and is most easily reached in topological semimetals due to their low carrier density. Here, the authors study this regime in the Dirac semimetal ZrTe₅ and find evidence for a Lifshitz transition at moderate field, leading to the emergence of a 1D-Weyl band structure at high field.

A versatile methodology to detect topological quasiparticles by transport measurements remains an open problem. Here, the authors propose and experimentally observe the temperature dependence of the quantum oscillation frequency as a signature of non-trivial band topology.

An approach to design compensated ferrimagnetic Heusler alloys is established. A small lack of compensation produces giant exchange bias and large coercivity. This effect is observed for alloys that have the magnetic transition above room temperature.

A 3D quantum Hall effect has been reported in Dirac semimetal ZrTe₅ due to a magnetic-field-driven Fermi surface instability. Here, the authors show evidence of quasi-quantized Hall response without Fermi surface instability, but they argue that it is due to the interplay of the intrinsic properties of ZrTe₅ electronic structure and Dirac semi-metallic character.

Quantized circular photogalvanic effect (CPGE) is predicted in chiral topological semimetals, but the experimental observation remains challenging. Here, Ni et al. observe a large topological longitudinal photocurrent in CoSi, which is much larger than the photocurrent in any other chiral crystals, indicating quantized CPGE within reach upon doping and increase of the hot-carrier lifetime.

A good way to identify microscopic conduction regimes where current flow deviates from Ohm’s law is still lacking. Here, the authors identify Sondheimer oscillations as a quantitative probe of the length scale of relaxing electron scattering in studying the non-ohmic electron flow of WP₂ crystals.

In all experimentally observed Weyl semimetals so far, the Weyl points always appear in pairs in the momentum space. Here, the authors report one unpaired Weyl point without surface Fermi arc emerging at the center of the Brillouin zone, which is surrounded by charged Weyl nodal walls in PtGa.

It is predicted that topological phase transitions in quantum materials can be triggered by selective excitation of coherent phonons. Upon excitation of a shear mode, Hein et al. observe distinct perturbations of electronic Weyl semimetal fingerprints in Td-WTe₂.

Endowing metal–organic frameworks with both high electrical conductivity and magnetic ordering could make such materials useful for spintronics. Here the authors design a layer-stacking coronene-based 2D MOF that exhibits a semiconducting feature with an electrical conductivity of ~10 S cm⁻¹ at 300 K, as well as ferromagnetism below ~20 K.

Semiconducting metal–organic frameworks (MOFs) can be of interest for optoelectronics, but charge transport property is rarely elucidated. Here, a π–d conjugated 2D MOF shows band-like charge transport, with room-temperature mobility of 220 cm² V^–1 s^–1.

In magnetic shape memory Heusler alloys, the premartensite phase is believed to be a precursor state of the martensite phase with preserved austenite phase symmetry. Here, the authors show that the premartensite is a stable phase with its own crystallographic symmetry resulting from the stepped growth of Bain distortions in the lattice.

Advances in the fabrication of low-disorder metallic materials have made it possible to reach the hydrodynamic regime of electronic transport. Here the authors investigate a hydrodynamic electron fluid in tungsten diphosphide and find that both electrical and thermal transport are limited by the quantum indeterminacy.

Bi₂TeI is identified as a dual topological insulator. It is a weak topological insulator with metallic states at the (010) surfaces and a topological crystalline insulator at the (001) surfaces.

There is a long-standing experimental effort to observe field-induced correlated states in three-dimensional materials. Here, the authors observe an unconventional Hall response in the quantum limit of the bulk semimetal HfTe₅ with a plateau-like feature in the Hall conductivity.

Optic atrophy 1 (OPA1) is known to be important for mitochondrial fusion and structural integrity. Here, using OPA1 knockout mice, the authors show a detrimental effect on host defense capabilities against pathogen infections. This study reports a critical role for OPA1 in innate immunity.

A complete electronic band theory is presented that describes the global properties of all possible band structures and materials, and can be used to predict new topological insulators and semimetals.

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

Defect engineering in topological materials is a frontier that promises tunable physical properties with rich applications. Here, the authors demonstrate the atomically precise engineering of vacancies in a topological semimetal, which locally tunes the magnetic properties.