Spin-Polarized Scanning Tunneling Microscopy Measurements of an Anderson Impurity.

We report spin-polarized scanning tunneling microscopy measurements of an Anderson impurity system in MoS_{2} mirror-twin boundaries, where both the quantum-confined impurity state and the Kondo resonance resulting from the interaction with the substrate are accessible. Using a spin-polarized tip, we observe magnetic-field-induced changes in the peak heights of the Anderson impurity states as well as in the magnetic-field-split Kondo resonance. Quantitative comparison with numerical renormalization group calculations provides evidence of the notable spin polarization of the spin-resolved impurity spectral function under the influence of a magnetic field.

Engineering 2D Materials from Single-Layer NbS.

Starting from a single layer of NbS grown on graphene by molecular beam epitaxy, the single unit cell thick 2D materials NbS-2D and NbS-2D are created using two different pathways. Either annealing under sulfur-deficient conditions at progressively higher temperatures or deposition of increasing amounts of Nb at elevated temperature result in phase-pure NbS-2D followed by NbS-2D. The materials are characterized by scanning tunneling microscopy, scanning tunneling spectroscopy, and X-ray photoemission spectroscopy.

2D Vanadium Sulfides: Synthesis, Atomic Structure Engineering, and Charge Density Waves.

Two ultimately thin vanadium-rich 2D materials based on VS are created via molecular beam epitaxy and investigated using scanning tunneling microscopy, X-ray photoemission spectroscopy, and density functional theory (DFT) calculations. The controlled synthesis of stoichiometric single-layer VS or either of the two vanadium-rich materials is achieved by varying the sample coverage and sulfur pressure during annealing. Through annealing of small stoichiometric single-layer VS islands without S pressure, S-vacancies spontaneously order in 1D arrays, giving rise to patterned adsorption.

Unconventional Charge-Density-Wave Gap in Monolayer NbS.

Using scanning tunneling microscopy and spectroscopy, for a monolayer of transition metal dichalcogenide H-NbS grown by molecular beam epitaxy on graphene, we provide unambiguous evidence for a charge density wave (CDW) with a 3 × 3 superstructure, which is not present in bulk NbS. Local spectroscopy displays a pronounced gap on the order of 20 meV at the Fermi level. Within the gap, low-energy features are present.