Search

Monolayers of transition metal dichalcogenides have emerged as interesting two-dimensional materials. Here, the authors show that in a new member of this family of compounds, rhenium disulphide, the layers in the bulk are vibrationally and electronically decoupled, so that they behave almost as monolayers.

The authors observe the signatures of quadrupolar excitons in a WSe₂-WS₂-WSe₂ trilayer moiré superlattice, originating from the hybridization of the WSe₂ valence moiré flatbands. They further use electrostatic gating to reveal a hybridized interlayer Mott insulator state, with holes shared between the two WSe₂ layers but laterally confined in moiré superlattices.

Heterobilayers of transition metal dichalcogenides host moiré superlattices that give rise to strong electron interactions. Here, the authors study the photoluminescence from interlayer excitons in a WS₂/WSe₂ heterobilayer to reveal the onset of various correlated insulating states.

Transition metal trichalcogenides are layered materials with strong in-plane anisotropy, and their vibrational characteristics remain largely unexplored. Here, the authors present high-pressure Raman studies to uncover unusual vibrational effects within this specific class of materials.

Single atomic layers of transition metal dichalcogenides are semiconductors with possible applications in spintronics. Here, the authors demonstrate tuning of the spin-orbit splitting in molybdenum tungsten diselenide by altering the alloy’s composition, impacting valley polarization and light emission yield.

Understanding the dynamics of light-induced carriers is vital for employing two-dimensional materials in optoelectronic applications. Here, the authors use a sub diffraction-limit optical technique to reveal the excitonic properties of monolayer molybdenum disulfide at the nanoscale.

Atomically thin transition metal dichalcogenides are an ideal platform to investigate the underlying physics of strongly bound excitons in low dimensions. Here, the authors demonstrate the formation of a bosonic condensate driven by excitons in two-dimensional MoSe₂ strongly coupled to light in a solid-state resonator.

Multi-exciton states may emerge in atomically thin transition metal dichalcogenides as a result of strong many-body interactions. Here, the authors report experimental evidence of four- and five-particle biexciton complexes in monolayer WSe₂ and their electrical control.

Here, the authors show that the interaction between microcavity photons and excitons in an atomically thin WSe₂ results in a hybridized regime of strong light-matter coupling. Coherence build-up is accompanied by a threshold-like behaviour of the emitted light intensity, which is a fingerprint of a polariton laser effect.

A coherent condensate of exciton–polaritons, extending spatially up to 4 µm and spin-polarizable with an external magnetic field, is observed at cryogenic temperatures in a MoSe₂ monolayer embedded in a vertical microcavity.

Alloys of two-dimensional materials normally occur when two components crystallize in the same phase. Here, the authors observe an anomalous phase instability, accompanied by a band bowing effect, in GaSe_1-xTe _x alloys on GaAs(111).

Due to the crystal symmetry of single-layer transition metal dichalcogenides and the fact that the conduction and valence band edges are at the zone-edge K points, the 2p exciton states are split. A two-colour pump–probe scheme is used to drive the 1s–2p exciton transition, and then probe the changes in absorption near the spectral position of the 1s line to measure the splitting energy.

Moiré superlattice exciton states are observed in WSe₂/WS₂ heterostructures with closely aligned layers.

Stacked 2D materials can host excitons with distinct valley selection rules due to the spatial variation of the moiré pattern. The authors demonstrate this via optical spectroscopy, opening a route for control of optoelectronic devices.

Scanning tunnelling spectroscopy and ab initio simulations reveal buckling reconstruction and in-plane strain redistribution in WSe₂/WS₂ moiré heterostructures.

The emergence of optically silent phonons show that strong interlayer electron–phonon coupling can arise in van der Waals heterostructures, with the vibrational modes in one layer coupling to the electronic states in a neighbouring layer.

The charge transfer between two layers of different two-dimensional materials occurs at a much faster speed than expected, holding promise for efficient optoelectronic devices.

Moiré superlattices offer a tunable platform for studying charge and spin phenomena in correlated solid-state systems. Here, the authors explore spin transport in twisted WSe₂/WS₂ superlattices and find signatures of spin–charge transport decoupling.

Interactions between excitons and correlated electrons can lead to the formation of interesting states. Now, evidence suggests that these interactions can give rise to a Mott insulator of excitons.

By combining large-scale first-principles GW-BSE calculations and micro-reflection spectroscopy, the nature of the exciton resonances in WSe₂/WS₂ moiré superlattices is identified, highlighting non-trivial exciton states and suggesting new ways of tuning many-body physics.

Layer-stacking domain walls in van der Waals heterostructures form a broadly tunable Luttinger liquid system, including both isolated and coupled arrays.

A novel scanning single-electron charging spectroscopy enables nanometre-scale imaging of quasiparticle excitations and thermodynamic gaps in generalized Wigner crystals.

The authors combine laser excitation and scanning tunnelling spectroscopy to visualize the electron and hole distributions in photoexcited moiré excitons in twisted bilayer WS₂. This photocurrent tunnelling microscopy approach enables the study of photoexcited non-equilibrium moiré phenomena at atomic scales.

Transition metal dichalcogenide bilayers offer a novel platform for studying correlated electron-hole fluids. Here the authors use optical spectroscopy to probe thermodynamic properties of coupled electron-hole states in MoSe₂/hBN/WSe₂ heterostructures, providing evidence for an excitonic insulator ground state.

An out-of-plane magnetic field is expected to strongly modify exciton-phonon interactions in atomically thin transitional metal dichalcogenides. Here, the authors show that the phonon-exciton interaction in monolayer WSe₂ lifts the inter-Landau-level transition selection rules for dark trions.

The moiré lattice of trilayer WSe₂ and monolayer WS₂ host interlayer excitons localized at different moiré sites. Using an electric field, the authors tune the superposition between two moiré sites via hybridization with intralayer excitons in WSe₂.

Understanding the flow of heat in materials just one or a few atoms thick is vital for harnessing them in compact electronic devices. Here, the authors present the temperature-dependent thermal conductivity of black phosphorus ribbons and demonstrate an intrinsic orientation dependence.

Twisted heterostructures of transition metal dichalcogenides host the so-called moiré excitons, or intralayer excitons modified by the moiré potential. Here the authors show tunability of the moiré excitons and the coexisting correlated electronic states in WSe₂/WS₂ superlattices with varying WSe₂ layer thickness

When independent layers of electrons and holes are in close proximity to each other, their Coulomb interaction allows them to pair into neutral bosons and form an insulating state. This phenomenon is reported in a heterostructure of 2D materials.

So far, only indirect evidence of Wigner crystals has been reported, but a specially designed scanning tunnelling microscope is used here to directly image them in a moiré heterostructure.

Here, the authors show brightening of dark excitons by strong coupling between cavity photons and high energy, spin-allowed, bright excitons in monolayer WSe₂. In this regime, the commonly observed photoluminescence quenching stemming from the fast relaxation to the dark ground state is prevented.

Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe₂/WS₂ moiré superlattices, and their electrical properties and excited spin states are studied using an optical technique.

The long lifetime and spin properties of dark excitons in atomically thin transition metal dichalcogenides offer opportunities to explore light-matter interactions beyond electric dipole transitions. Here, the authors demonstrate that the coupling of the dark exciton and an optically silent chiral phonon enables the intrinsic photoluminescence of the dark-exciton replica in monolayer WSe₂

The integration of a TMDC monolayer into a high-Q microcavity enables the observation of optical valley Hall effect.

A lateral heterojunction with diode-like electrical transport can be created in a homogeneous MoS₂ monolayer by using a substrate in which one segment is made from an amorphous fluoropolymer and another segment from hexagonal boron nitride.

The optical and electronic properties of semiconducting transition metal dichalcogenides are strongly dependent on native defects within their crystal lattice. Here, the authors use transient spectroscopy to identify defect-related deep levels in the bandgap of MoS₂, WS₂ and their alloys.

Tunable X-ray generation, from ultrathin van der Waals materials impacted by relativistic electrons, is demonstrated.

Graphene oxide sheets hold promise for a variety of applications but are disordered and inhomogeneous on synthesis. Although processes to resolve this exist they typically remove oxygen groups, affecting the sheets’ properties. Now, a scalable, mild thermal annealing procedure has been devised that enhances the optical and electronic properties of graphene oxide sheets through phase transformation, while preserving their oxygen functionality.

The Hubbard model describes many fascinating phenomena, but relating it to complicated quantum materials is difficult. Now, atomic-resolution measurements can estimate the interaction parameters that appear in the model for real materials.

Stacking monolayer WS₂ on top of bilayer WSe₂ creates conditions where electrons and holes can coexist in the structure. Their Coulomb interaction allows them to form bound pairs and hence an excitonic insulator state.

Light–matter interactions in monolayer MoSe₂ can be dramatically modified by the interactions between the excitonic states, leading to a rich set of light-driven coherent phenomena.