Interlayer Exciton-Phonon Coupling in MoSe/WSe Heterostructures.

Transition metal dichalcogenide heterostructures have garnered strong interest for their robust excitonic properties, mixed light-matter states such as exciton-polaritons, and tailored properties, vital for advanced device engineering. Two-dimensional heterostructures inherit their physics from monolayers with the addition of interlayer processes that have been particularly emphasized for their electronic and optical properties. Here, we demonstrate the interlayer coupling of the MoSe phonons to WSe excitons in a WSe/MoSe heterostructure using resonant Raman scattering.

Interfacial Distortion of SbTe-SbSe Multilayers via Atomic Layer Deposition for Enhanced Thermoelectric Properties.

Atomic layer deposition (ALD) is an effective technique for depositing thin films with precise control of layer thickness and functional properties. In this work, SbTe-SbSe nanostructures were synthesized using thermal ALD. A decrease in the SbTe layer thickness led to the emergence of distinct peaks from the Laue rings, indicative of a highly textured film structure with optimized crystallinity.

Strong Dipolar Repulsion of One-Dimensional Interfacial Excitons in Monolayer Lateral Heterojunctions.

Repulsive and long-range exciton-exciton interactions are crucial for the exploration of one-dimensional (1D) correlated quantum phases in the solid state. However, the experimental realization of nanoscale confinement of a 1D dipolar exciton has thus far been limited. Here, we demonstrate atomically precise lateral heterojunctions based at transitional-metal dichalcogenides (TMDCs) as a platform for 1D dipolar excitons.

Impact of anion polarizability on ion pairing in microhydrated salt clusters.

Despite longstanding interest in the mechanism of salt dissolution in aqueous media, a molecular level understanding remains incomplete. Here, cryogenic ion trap vibrational action spectroscopy is combined with electronic structure calculations to track salt hydration in a gas phase model system one water molecule at a time. The infrared photodissociation spectra of microhydrated lithium dihalide anions [LiXX'(HO) ] (XX' = I, ClI and Cl; = 1-3) in the OH stretching region (3800-2800 cm) provide a detailed picture of how anion polarizability influences the competition among ion-ion, ion-water and water-water interactions.

Stacking Polymorphism in PtSe Drastically Affects Its Electromechanical Properties.

PtSe is one of the most promising materials for the next generation of piezoresistive sensors. However, the large-scale synthesis of homogeneous thin films with reproducible electromechanical properties is challenging due to polycrystallinity. It is shown that stacking phases other than the 1T phase become thermodynamically available at elevated temperatures that are common during synthesis.

Phosphoric Acid Catalyzed Formation of Hydrogen-Bonded -Quinone Methides. Enantioselective Cycloaddition with β-Dicarbonyl Compounds toward Benzannulated Oxygen Heterocycles.

A full account of the Brønsted acid catalyzed, enantioselective synthesis of 4-chromenes and 1-xanthen-1-ones from -hydroxybenzyl alcohols and β-dicarbonyl compounds is provided. The central step of our strategy is the BINOL-phosphoric acid catalyzed, enantioselective cycloaddition of β-diketones, β-keto nitriles, and β-keto esters to in situ generated, hydrogen-bonded -quinone methides. Upon acid-promoted dehydration, the desired products were obtained with generally excellent yields and enantioselectivity.

Stone-Wales Defects Cause High Proton Permeability and Isotope Selectivity of Single-Layer Graphene.

While the isotope-dependent hydrogen permeability of graphene membranes at ambient condition has been demonstrated, the underlying mechanism has been controversially discussed during the past 5 years. The reported room-temperature proton-over-deuteron (H -over-D ) selectivity is 10, much higher than in any competing method. Yet, it has not been understood how protons can penetrate through graphene membranes-proposed hypotheses include atomic defects and local hydrogenation.

Twist-angle-dependent interlayer exciton diffusion in WS-WSe heterobilayers.

The nanoscale periodic potentials introduced by moiré patterns in semiconducting van der Waals heterostructures have emerged as a platform for designing exciton superlattices. However, our understanding of the motion of excitons in moiré potentials is still limited. Here we investigated interlayer exciton dynamics and transport in WS-WSe heterobilayers in time, space and momentum domains using transient absorption microscopy combined with first-principles calculations.

Electron-phonon-driven three-dimensional metallicity in an insulating cuprate.

The role of the crystal lattice for the electronic properties of cuprates and other high-temperature superconductors remains controversial despite decades of theoretical and experimental efforts. While the paradigm of strong electronic correlations suggests a purely electronic mechanism behind the insulator-to-metal transition, recently the mutual enhancement of the electron-electron and the electron-phonon interaction and its relevance to the formation of the ordered phases have also been emphasized. Here, we combine polarization-resolved ultrafast optical spectroscopy and state-of-the-art dynamical mean-field theory to show the importance of the crystal lattice in the breakdown of the correlated insulating state in an archetypal undoped cuprate.

Artificial relativistic molecules.

We fabricate artificial molecules composed of heavy atom lead on a van der Waals crystal. Pb atoms templated on a honeycomb charge-order superstructure of IrTe form clusters ranging from dimers to heptamers including benzene-shaped ring hexamers. Tunneling spectroscopy and electronic structure calculations reveal the formation of unusual relativistic molecular orbitals within the clusters.

Atomic and electronic structure of trilayer graphene/SiC(0001): Evidence of Strong Dependence on Stacking Sequence and charge transfer.

The transport properties of few-layer graphene are the directly result of a peculiar band structure near the Dirac point. Here, for epitaxial graphene grown on SiC, we determine the effect of charge transfer from the SiC substrate on the local density of states (LDOS) of trilayer graphene using scaning tunneling microscopy/spectroscopy and angle resolved photoemission spectroscopy (ARPES). Different spectra are observed and are attributed to the existence of two stable polytypes of trilayer: Bernal (ABA) and rhomboedreal (ABC) staking.

Evidence for Flat Bands near the Fermi Level in Epitaxial Rhombohedral Multilayer Graphene.

The stacking order of multilayer graphene has a profound influence on its electronic properties. In particular, it has been predicted that a rhombohedral stacking sequence displays a very flat conducting surface state: the longer the sequence, the flatter the band. In such a flat band, the role of electron-electron correlation is enhanced, possibly resulting in high Tc superconductivity, magnetic order, or charge density wave order.