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The interplay between dark and bright excitons has a significant impact on the optical properties of semiconducting transition metal dichalcogenides. Here, the authors perform computational and experimental studies which unveil the microscopic origin of the excitonic coherence lifetime in WS₂ and MoSe₂.

High-order correlated states in atomically thin transition metal dichalcogenides may be facilitated by long-lived optically dark excitons. Here, the authors report experimentally the emergence of neutral and charged biexciton species at low light intensities in encapsulated WSe₂ monolayers.

A detailed understanding of the response of graphene resonators to changes in mass and temperature could lead to the development of ultrasensitive mass detectors and other nanoelectromechanical systems.

Atomically thin layers of transition metal dichalcogenides are shown to exhibit a disappearance of strong excitonic absorption along with population inversion at the direct gap over a spectral range of hundreds of meV after pulsed photoexcitation.

Researchers clarify damping pathways for mid-infrared graphene plasmons, including graphene intrinsic optical phonons and edge scattering. They also demonstrate the guiding of mid-infrared graphene plasmons in 50-nm-wide structures with an electromagnetic mode area of 10⁻³μm² and a propagation length of 200 nm.

The authors report the emergence of quadrupolar excitons in angle-aligned WSe₂/WS₂/WSe₂ heterotrilayers characterized by a delocalized hole residing in both outer WSe₂ layers, electric-field tunability and reduced exciton–exciton interactions.

Monolayer graphene has no electronic band gap. Bilayer graphene does, and can be controlled by an electric field. And for trilayer graphene, infrared transmission measurements indicate both situations are possible depending on the stacking of the layers.

Graphene, an atom-thin carbon sheet is interesting for its fundamental properties as well as for its possible applications in electronics, is not strictly two-dimensional. Microscopic corrugations, or ripples, have been observed in all graphene sheets so far. Direct experimental study of the physics of such ripples has been hindered by the lack of flat graphene layers. Ultraflat graphene is now achieved through its deposition on the atomically flat terraces of cleaved mica surfaces.

Circularly polarized light has been used to confine charge carriers in single-layer molybdenum disulphide entirely to a single energy-band valley, representing full valley polarization.

A global network of researchers was formed to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity; this paper reports 13 genome-wide significant loci and potentially actionable mechanisms in response to infection.

Magnetic brightening enables direct observation of spin-forbidden dark excitons in a monolayer WSe₂.

A genome-wide association study including over 76,000 individuals with schizophrenia and over 243,000 control individuals identifies common variant associations at 287 genomic loci, and further fine-mapping analyses highlight the importance of genes involved in synaptic processes.

Researchers demonstrate a method based on circularly polarized laser-field-driven high-harmonic generation for probing non-trivial and trivial topological phases in a three-dimensional topological insulator.

Here, the authors show that longer duration and greater degree of overweight and obesity during early adulthood as well as younger age of onset of a high body mass index are associated with a higher risk of 18 cancer types.

Electronic band topology may be leveraged to enhance nonlinear optical properties in monolayer semiconductors. Here, the authors report giant room-temperature nonlinearity enhancements in Janus transition metal dichalcogenides.

Optical experiments on WSe₂/MoSe₂ heterobilayers reveal signatures of moiré trions, including interlayer emission with sharp lines and a complex charge-density dependence, features that differ markedly from those of conventional trions.

Strong many-body Coulomb interactions allow for bound two- and three-body excitonic states to form in monolayer transition metal dichalcogenides, but it is now shown that such interactions are strong enough to create four-body biexcitonic states.

A chip-integrated graphene photodetector with a high responsivity of over 0.1 A W⁻¹, high speed and broad spectral bandwidth is realized through enhanced absorption due to near-field coupling. Under zero-bias operation, response rates above 20 GHz and an instrumentation-limited 12 Gbit s⁻¹ optical data link are demonstrated.

In heterostructures of the transition metal dichalcogenides MoS₂ and WSe₂, atomically thin p–n junctions are created that show gate-tunable rectifying and photovoltaic behaviour mediated by tunnelling-assisted interlayer recombination.

Electrically biased suspended graphene devices show an intense electroluminescence in the visible range with a tunable emission spectrum.

The appealing electronic properties of the monolayer semiconductor molybdenum disulphide make it a candidate material for electronic devices. The observation of tightly bound trions in this system—which have no analogue in conventional semiconductors—opens up possibilities for controlling these quasiparticles in future optoelectronic applications.

Observations of high-harmonic generation from a single layer of a transition metal dichalcogenide opens the door to studying strong-field and attosecond phenomena in two-dimensional materials.

Valleys in momentum space provide a degree of freedom that could be exploited for applications. A demonstration of valley pseudospin control now completes the generation–manipulation–detection paradigm, paving the way for valleytronic devices.

Electronic bandgap tuning in semiconductors enables key functionalities in solid-state devices. Here, the authors present a strategy to control the bandgap of atomically thin WS₂ and WSe₂semiconductors via manipulation of the surrounding dielectric environment rather than by modifications of the materials themselves.

Imaging the electron and hole that bind to form interlayer excitons in a 2D moiré material enables direct measurement of its diameter and indicates the localization of its centre of mass.

Here, the authors show the formation of exciton-polaritons with enhanced nonlinear response using excited excitonic Rydberg states in monolayer WSe₂ embedded in a microcavity.

Local changes of the Coulomb interaction due to external dielectric environment fluctuations present a new type of disorder in monolayer transition-metal dichalcogenides.

Defects in hexagonal boron nitride exhibit room-temperature quantum emission, but their unknown structural origin challenges their technological utility. A combination of optical and electron microscopy helps to distinguish at least four classes of defects and correlate them with local strain.

Electron–phonon coupling in a monolayer WSe₂ on a substrate is investigated by femtosecond surface X-ray scattering. Counterintuitively, the absorbed optical photon energy is dominantly coupled to the in-plane lattice vibrations within 1 ps.

Despite recent progress in the synthesis and characterization of molybdenum disulphide, little is yet known about its microstructure. Using refined chemical vapour deposition synthesis, high-quality crystals of monolayer molybdenum disulphide have now been grown. Single-crystal islands and polycrystals containing tilt and mirror twin grain boundaries are characterized, and the influence of the grain boundaries on the material properties of molybdenum disulphide is assessed.

Liquid ultrafast electron scattering measures structural responses in liquid water with femtosecond temporal and atomic spatial resolution to reveal a transient hydrogen bond contraction then thermalization preceding relaxation of the OH stretch.

This Review discusses the properties of polariton modes (plasmon, phonon and exciton) in graphene, hexagonal boron nitride and transition metal dichalcogenides for applications across the terahertz to visible spectrum.

The interaction of strong laser fields with tungsten disulfide leads to light-dressed Floquet replica of excitonic states, which manifest as new features in the transient absorption spectrum.

Femtosecond electron diffraction and ab initio theory unravel ultrafast lattice dynamics in photoexcited two-dimensional heterostructures during charge transfer.

Terahertz light pulses induce transitions between a topological and a trivial phase in the Weyl semimetal WTe₂ through an interlayer shear strain.

This Review discusses recent experimental and theoretical efforts in electron dynamics in TMDC heterostructures and the relevance of these effects for potential applications in optoelectronic and valleytronic/spintronic devices.

The two-dimensional semiconducting material molybdenum disulphide shows strong piezoelectricity in its single-layered form, suggesting possible applications in nanoscale electromechanical devices for sensing and energy harvesting.

Understanding the physics of two-dimensional materials beyond graphene is of both fundamental and practical interest. Recent theoretical and experimental advances uncover the interplay between real spin and pseudospins in layered transition metal dichalcogenides.