Observation of topologically protected states at crystalline phase boundaries in single-layer WSe.

Transition metal dichalcogenide materials are unique in the wide variety of structural and electronic phases they exhibit in the two-dimensional limit. Here we show how such polymorphic flexibility can be used to achieve topological states at highly ordered phase boundaries in a new quantum spin Hall insulator (QSHI), 1T'-WSe. We observe edge states at the crystallographically aligned interface between a quantum spin Hall insulating domain of 1T'-WSe and a semiconducting domain of 1H-WSe in contiguous single layers.

Substrate-induced enhancement of the chemical reactivity in metal-supported graphene.

Graphene is commonly regarded as an inert material. However, it is well known that the presence of defects or substitutional hetero-atoms confers graphene promising catalytic properties. In this work, we use first-principles calculations to show that it is also possible to enhance the chemical reactivity of a graphene layer by simply growing it on an appropriate substrate.

Unveiling the atomistic mechanisms for oxygen intercalation in a strongly interacting graphene-metal interface.

The atomistic mechanisms involved in the oxygen (O) intercalation in the strongly interacting graphene (G) on Rh(111) system are characterized in a comprehensive experimental and theoretical study, combining scanning tunneling microscopy and density functional theory (DFT) calculations. Experimental evidence points out that the G areas located just above the metallic steps of the substrate are the active sites for initializing the intercalation process when some micro-etching points appear after molecular oxygen gas exposure. These regions are responsible for both the dissociation of the oxygen molecules and the subsequent penetration to the G-metal interface.

Purely substitutional nitrogen on graphene/Pt(111) unveiled by STM and first principles calculations.

Nitrogen doping of graphene can be an efficient way of tuning its pristine electronic properties. Several techniques have been used to introduce nitrogen atoms on graphene layers. The main problem in most of them is the formation of a variety of C-N species that produce different electronic and structural changes on the 2D layer.

Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films.

High quality WSe2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2.

Tug-of-war between corrugation and binding energy: revealing the formation of multiple moiré patterns on a strongly interacting graphene-metal system.

The formation of multidomain epitaxial graphene on Rh(111) under ultra-high vacuum (UHV) conditions has been characterized by scanning tunnelling microscopy (STM) measurements and density functional theory (DFT) calculations. At variance with the accepted view for strongly interacting graphene-metal systems, we clearly demonstrate the formation of different rotational domains leading to multiple moiré structures with a wide distribution of surface periodicities. Experiments reveal a correlation between the STM apparent corrugation and the lattice parameter of the moiré unit cell, with corrugations of just 30-40 pm for the smallest moirés.

Trisomy 12 and p53 deletion in chronic lymphocytic leukemia detected by fluorescence in situ hybridization: association with morphology and resistance to conventional chemotherapy.

The incidence of trisomy 12 and p53 deletion was studied in a group of chronic B-lymphocytic leukemia (B-CLL) patients, using fluorescence in situ hybridization (FISH). Trisomy 12 was detected in eight of 50 patients (16%) and p53 deletion in six of 38 cases analyzed (15.8%).