Search

Fractional Chern insulators have been observed in moiré MoTe₂ at zero magnetic field, but the expected zero longitudinal resistance has not been demonstrated. Now it is shown that improving device quality allows this effect to appear.

Optical control of integer and fractional Chern insulators is demonstrated by circularly polarized optical pumping in tMoTe₂.

The authors study the field-induced ferromagnetic state of MnBi_2-xSb_xTe₄ by quantum oscillations and high-field Hall effect measurements. They confirm a single pair of type-II Weyl nodes, the long-sought “ideal” Weyl semimetal.

Topological materials hold great promise for dissipationless information transmission. Here, the authors create Chern insulator junctions between domains with different Chern numbers in MnBi₂Te₄ to realize the basic operation of a topological circuit.

The authors show that bichromatic moiré superlattices formed by two mismatched moiré patterns in van der Waals semiconductor heterotrilayers stabilize quadrupolar moiré trions and enable electric-field tuning of excitonic and electronic ground states.

The topological properties of twisted bilayer MoTe₂ are thought to stem from a spatial texture in the layer polarization of the electronic wavefunctions. This polarization is now measured using scanning tunnelling microscopy.

The authors find low-energy magnetic excitations and a flat band near the Fermi level in kagome metal superconductor CsCr3Sb5 by angle-resolved photoemission and resonant inelastic X-ray scattering. They suggest that the flat band plays a role in the emergence of charge/magnetic order at low temperatures.

Pressure-induced changes in the magnetic order of bilayer and trilayer van der Waals crystals are revealed and attributed to changes in the stacking arrangement.

In analogy with quantum Hall systems, it may be possible to find non-abelian anyons in the higher bands of Chern insulators. Now, the phase diagram of the second moiré band of twisted MoTe₂ is explored, laying the groundwork for such investigations.

The coupling between magnetism and topology is studied in a van der Waals heterostructure.

Metallic ferromagnetism is reported in an exfoliated monolayer of the van der Waals material Fe₃GeTe₂.

The speed with which symmetry breaking transitions occur in the solid state makes them difficult to study in the time domain. State-of-the-art pump–probe measurements of the dynamics of charge-density waves in terbium telluride enable the evolution of the symmetry breaking charge-order transition of this system to be studied with unprecedented temporal resolution.

For an ideal topological insulator, the metallic surface states should be easy to measure using transport techniques; however, the bulk is not completely insulating. Improving the ‘leaky’ bulk state proves crucial for measuring the surface Dirac fermions, including correlation effects.

The bulk–edge correspondence is directly imaged in a fractional Chern insulator at zero magnetic field with exciton-resonant microwave impedance microscopy, revealing spatially resolved bulk and edge characteristics, and the evolution of topological states in twisted MoTe₂.

Despite a significant amount of research, there are still many unknowns about the underlying mechanisms of the superconductivity in Fe-based superconductors, in particular the roles of magnetism and nematicity. Here, the authors investigate the compositional dependence of the nematic susceptibility in Fe_1+yTe_1−xSe_x and the interplay between nematic and spin fluctuations, as well as the effect of orbital differentiation on nematic instability.

Correlated materials can show nematicity, but the nematic state usually exhibits even-fold rotational symmetry. Now, a correlated antiferromagnet is shown to host a three-state Potts vestigial nematicity that can be controlled by external strain.

Niobium halide semiconductors are interesting for their breathing kagome geometry, easily exfoliable layered structure, and potential two-dimensional magnetism. Here, experimental evidence of flat bands in Nb₃I₈, originating from the niobium breathing kagome lattice, is observed using angle-resolved photoemission spectroscopy and supported by first-principles calculations.

Observations of strong electron correlation effects have been mostly confined to compounds containing f orbital electrons. Now, the study of the 3d pyrochlore metal CuV₂S₄ reveals that similar effects can be induced by flat-band engineering.

The controlled manipulation of the topological phases of electronic materials is a central goal of modern condensed matter research. Here, the authors demonstrate controllable switching between two distinct topological phases in a layered ferromagnet via thermal cycling.

Phonons are the collective excitations of the lattice of a material, and can, in the case of chiral phonons, carry angular momentum, allowing for strong coupling to the magnetic properties of the material. Here, Cui, Bostrom and co-authors observe chiral magnon polarons, the hybridized quasiparticles of chiral phonons and magnons, in the van der Waals antiferromagnet FePSe₃.

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.

Spin ice compounds are typically insulating and introducing carriers can destroy the spin ice state, making integration into electronic devices problematic. Here the authors report a transport response to an ice-rule-breaking transition in a heterostructure of a pyrochlore spin ice and a nonmagnetic metal.

Transport measurements in twisted bilayer MoTe₂ reveal quantized Hall resistance plateaus and composite Fermi liquid-like behaviour under zero magnetic field, constituting a direct observation of integer and fractional quantum anomalous Hall effects.

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.

Van der Waals materials are characterized by two dimensional layers weakly held together by interlayer van der Waals forces. Here, the authors study how shear motions between these layers influence the magnetic properties of the van der Waals antiferromagnets FePS3, MnPS3, and NiPS3. ‘

The authors combine simultaneous transport and X-ray diffraction measurements with in-situ tunable strain to measure the temperature dependence of the shear modulus and elastoresistivity above the nematic transition and the spontaneous orthorhombicity and resistivity anisotropy below the nematic transition of Co-doped BaFe₂As₂.

Exciton condensation has been observed in various three-dimensional (3D) materials. Now, monolayer WTe₂—a 2D topological insulator—also shows the phenomenon. Strong electronic interactions allow the excitons to form and condense at high temperature.

A cryo-strain device capable of applying large, continuous strains to two-dimensional materials in situ enables the reversible tuning of magnetic order and spin-canting process of the layered magnetic semiconductor CrSBr.

Exotic states emerge from the interplay between band topology and ferromagnetism, but it remains less known in canted-antiferromagnetic phase. Here, the authors realize a canted-antiferromagnetic Chern insulator in atomically-thin MnBi₂Te₄ with electrical control of chiral-edge state transport.

Spin-charge interactions are at the core of electronic correlation phenomena in Mott insulators. Here, the authors observe a positive anomalous magnetoresistance in a SrIrO₃/SrTiO₃ superlattice, indicative of strong spin-charge fluctuations in this pseudospin-half square-lattice Mott insulator.

Placing a single layer of tungsten diselenide in contact with twisted bilayer graphene enables superconductivity even for non-magic twist angles where insulating behavior is absent.

Using several ultrafast diffraction and microscopy techniques, demagnetization-driven interlayer shear of a van der Waals antiferromagnet is visualized at the nanoscale.

The anomalous Hall effect can signify that a material has a spontaneous magnetic order. Now, twisted bilayer graphene shows this effect at half filling, suggesting that the ground state is valley-polarized.

While two-dimensional semiconductors enable the investigation of light–matter interactions in low dimensions, a link to magnetic order has so far remained elusive. Now, the antiferromagnetic insulator NiPS₃ is found to exhibit excitons with strong linear polarization that are coupled to the zigzag antiferromagnetic order.

Using doped BaFe₂As₂, the authors test whether nematicity is linked to superconductivity in the iron pnictides by applying the conjugate field to nematicity—a specific form of strain—and observe that the critical temperature decreases.

Recent experiments utilizing strain have shed light on the role of electronic nematicity in determining the properties of unconventional superconductors. This Perspective reviews these developments and discusses open questions.

The underlying mechanism of iron-based superconductivity, the role of electron correlations, and the extent to which the behavior resembles those of the cuprates has been debated since their discovery. Here, using angle resolved photoemission spectroscopy, the authors report reconstruction of the Fermi surface for FeTe_1−xSe_x driven by orbital-dependent correlation effects in the absence of symmetry breaking and find evidence for an orbital-selective Mott transition.