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The interplay between reduced dimensionality and interactions in monolayer transition metal dichalcogenides has been of great research interest. Here the authors report an insulating dimer ground state in 1T-IrTe₂, driven by the combined effect of the charge density wave instability and local atomic bond formation.

Superconductivity is the result of many-body interactions between excitations in a solid. Zhang et al.use time- and angle-resolved photoemission to compare photo-induced changes in the electron self-energy of a unconventional superconductor to those in a related material in the metallic state.

A combination of photoemission and scanning tunnelling spectroscopy measurements provide compelling evidence that single layers of 1T'-WTe₂ are a class of quantum spin Hall insulator.

Previous work proposed the Berry curvature dipole as the mechanism of the nonlinear Hall effect. Lee et al. establish the sign-changing Berry curvature hot spots from spin-orbit split bands as the origin of the Berry curvature dipole and link it to the nonlinear Hall effect in the topological semimetal NbIrTe₄.

Signatures of an excitonic insulator have been reported in several two-dimensional materials. Here the authors report electronic properties of monolayer ZrTe₂ from ARPES and STM measurements that are consistent with the preformed exciton gas phase, a precursor for the excitonic insulator.

In a topological insulator, the surface-state electron spins are ‘locked’ to their direction of travel. But when an electron is kicked out by a photon through the photoelectric effect, the spin polarization is not necessarily conserved. In fact, the ejected spins can be completely manipulated in three dimensions by the incident photons.

Some quantum spin liquids are expected to have an effective Fermi surface of fractionalized spinon excitations. The two-dimensional spin liquid candidate 1T-TaSe₂ has charge density modulations that may be caused by an unstable spinon Fermi surface.

Stacking graphene in such a way that each layer is rotated relative to the one below provides a way of controlling the properties of this useful material. Park et al. now demonstrate a technique for fabricating this twisted graphene in such a way that it has an intrinsic electronic bandgap.

The nature of defects in transition metal dichalcogenide semiconductors is still under debate. Here, the authors determine the atomic structure and electronic properties of chalcogen-site point defects common to monolayer MoSe₂ and WS₂, and find that these are substitutional defects, where a chalcogen atom is substituted by an oxygen atom, rather than vacancies.