Search

In this paper we review a recently introduced microscopy technique, scanning quantum dot microscopy (SQDM), which delivers quantitative maps of local electrostatic potential near surfaces in three dimensions. The key to achieving SQDM imaging is the functionalization of a scanning probe microscope tip with a π-conjugated molecule that acts as a gateable QD. Mapping of electrostatic potential with SQDM is performed by gating the QD by the bias voltage applied to the scanning probe microscope junction and registering changes of the QD charge state with frequency-modulated atomic force microscopy.

We introduce the Computational 2D Materials Database (C2DB), which organises a variety of structural, thermodynamic, elastic, electronic, magnetic, and optical properties of around 1500 two-dimensional materials distributed over more than 30 different crystal structures. Material properties are systematically calculated by state-of-the art density functional theory and many-body perturbation theory (G$_0\!$W$\!_0$ and the Bethe-Salpeter Equation for $\sim$200 materials) following a semi-automated workflow for maximal consistency and transparency. The C2DB is fully open and can be browsed online or downloaded in its entirety. In this paper, we describe the workflow behind the database, present an overview of the properties and materials currently available, and explore trends and correlations in the data. Moreover, we identify a large number of new potentially synthesisable 2D materials with interesting properties targeting applications within spintronics, (opto-)electronics, and plasmonics. The C2DB offers a comprehensive and easily accessible overview of the rapidly expanding family of 2D materials and forms an ideal platform for computational modeling and design of new 2D materials and van der Waals heterostructures., Comment: Add journal reference and DOI; Minor updates to figures and wording

Monolayers and bilayers of transition metal dichalcogenides (TMDCs) are currently being intensively scrutinized not least due to their rich opto-electronic properties which are governed by strongly bound excitons. Until now the main focus has been on excitons with zero momentum. In this study we employ ab initio many-body perturbation theory within the GW/BSE approximation to describe the entire Q-resolved exciton band structure for mono- and bilayers of the MX2 (M = Mo, W and X = Se, S) TMDCs. We find that the strong excitonic effects, i.e. strong electron-hole interactions, are present throughout the entire Q-space. While the exciton binding energies of the lowest excitons do not vary significantly with Q, we find a strong variation in their coupling strength. In particular, the latter are strongly peaked for excitons at Q = 0 and Q = Λ. For MoX2 monolayers the K → K' excitons constitutes the exciton ground state, while in WX2 monolayers direct transitions at K are lowest in energy. Our calculations further show that the exciton landscape is highly sensitive to strain and interlayer hybridization. For all four bilayers the exciton ground state is shifted to Γ → Λ or K → Λ transitions closely following the trends of the single-particle band structures.