Stark shift and electric-field-induced dissociation of excitons in monolayer MoS2 and hBN/MoS2 heterostructures

Efficient conversion of photons into electrical current in two-dimensional semiconductors requires, as a first step, the dissociation of the strongly bound excitons into free electrons and holes. Here we calculate the dissociation rates and energy shift of excitons in monolayer MoS2 as a function of an applied in-plane electric field. The dissociation rates are obtained as the inverse lifetime of the resonant states of a two-dimensional hydrogenic Hamiltonian which describes the exciton within the Mott-Wannier model. The resonances are computed using complex scaling, and the effective masses and screened electron-hole interaction defining the hydrogenic Hamiltonian are computed from first principles. For field strengths above 0.1 V/nm the dissociation lifetime is shorter than 1 ps, which is below the lifetime associated with competing decay mechanisms. Interestingly, encapsulation of the MoS2 layer in just two layers of hexagonal boron nitride (hBN), enhances the dissociation rate by around one order of magnitude due to the increased screening. This shows that dielectric engineering is an effective way to control exciton lifetimes in two-dimensional materials

Dissociation of two-dimensional excitons in monolayer WSe₂

In two-dimensional semiconductors excitons are strongly bound, suppressing the creation of free carriers. Here, the authors investigate the main exciton dissociation pathway in p-n junctions of monolayer WSe2 by means of time and spectrally resolved photocurrent measurements

The Computational 2D Materials Database: High-Throughput Modeling and Discovery of Atomically Thin Crystals

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 wordin

An application for the automatic phasing of quarter wave cavities at HIE ISOLDE

The HIE upgrade at ISOLDE will use 32 independently phased superconducting quarter wave cavities, and aims to study a large range of different radioactive species. The broad experimental programme means that the same beam species and energy are rarely studied twice, and hence the linac must be rephased for each experiment. In order to speed up this process, an automatic phasing routine has been developed which takes as input the properties of the beam and the linear accelerator as well as the desired final energy, and calculates the necessary phases and voltages on each cavity. The phasing routine has also been used to better understand the longitudinal beam dynamics and how errors and uncertainties will affect phasing of the cavities, leading to a set of tolerances for each of the different linac parameters

Influence of Safety Measures on the Risks of Transporting Dangerous Goods through Road Tunnels.

Abstract not availableJRC.G-Institute for the Protection and the Security of the Citizen (Ispra

Regulatory Requirements for Biocides on the Market in the European Union According to Directive 98/8/EC.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra