Olga Lopez-Acevedo is an Academy Fellow and Group Leader in the Centre of Excellence on Computational Nanosciences, Aalto University, Finland. Her postdoctoral experience includes stays at the Université Libre de Bruxelles, Belgium, and University of Jyväskylä, Finland. In 2006, she obtained a PhD in theoretical physics working on quantum algorithmics from the University of Cergy-Pontoise, France. She obtained her Bachelor’s and Master’s degrees in physics from the University of Strasbourg, France. Her research interest focuses on the quantum modeling of hybrid soft-nano systems and the development of computational methods for multi-scale simulations. k F is essentially constant (dashed purple line shows the average value) and 2.96 × 10 14 electrons/ cm 2 remain within the ( 2 × 2)-K adlayer.Published by De Gruyter MaOn the interaction between gold and silver metal atoms and DNA/RNA nucleobases – a comprehensive computational study of ground state properties (e) Extracted Fermi wave vector k F as a function of polar angle ϕ along the pocket. (d) Parabola fit (purple curve) to the spectral MDC (gray circles) and EDC maxima (orange squares). The dispersion is consistent with the free-electron-like expectation for K 4 s. (c) 3D view of the potassium-induced band at Γ ¯. 1 × 1 (dotted red) and 2 × 2 (dotted purple) BZs of graphene are also indicated. (b) Schematized Fermi surface highlighting the original π * pockets (solid red) with their 2 × 2 replicas (dashed red) and the circular contours (solid purple). Aside from the intense π * pockets around K ¯ gr, a potassium-induced circular contour around Γ ¯ as well as graphene replicas emerge, both repeating with a 2 × 2 periodicity relative to the graphene lattice. The latter data set was obtained for k y < 0 and mirrored along k y = 0 for visualization purposes. (a) Experimental Fermi surface after potassium deposition probed over a wide range of parallel momenta at h ν = 110 eV (bottom) and 140 eV (top). (e), (f) The carrier density of graphene increases by 1.26 × 10 14 cm − 2 as determined from the area enclosed by its Fermi surface pockets (e) before and (f) after potassium deposition. Additional spectral weight appearing below 2 eV in (d) can be attributed to ionized potassium . Concomitantly, the elongated region around the Dirac point is reshaped (cf. Owing to n-type charge-transfer doping, the Dirac point binding energy E D increases by 0.59 eV while the Ag valence band undergoes a rigid shift of only 0.26 eV. (c), (d) Same as (a), (b) after 7 min of potassium deposition. Enhanced contrast at the bottom center of (b) reveals replica bands of Ag (white arrows) backfolded via graphene reciprocal lattice vectors. The VHS at M ¯ Ag splits up into two peaks (fitted EDC in the top inset). (a), (b) Energy-momentum cuts for pristine graphene/Ag/SiC slicing (a) the graphene Dirac cone at K ¯ gr, perpendicular to Γ K ¯ gr and (b) the Ag valence band along the KMK ¯ border of its BZ. Our results establish surface charge-transfer doping as an efficient handle to modify band alignment and electronic properties of a van der Waals heterostructure assembled from graphene and a novel type of monolayered quantum material. We further demonstrate an ordered potassium adlayer ( 2 × 2 relative to graphene) with free-electron-like dispersion, suppressing plasmaron quasiparticles in graphene via enhanced metallization of the heterostack. While the induced carrier densities on the order of 10 14 cm − 2 are not yet sufficient to reach the onset of the silver conduction band, the band alignment of graphene changes relative to the rigidly shifting Ag valence band and substrate core levels. Here, we n-type dope a graphene/2D-Ag/SiC heterostack via in situ potassium deposition and probe its band structure by means of synchrotron-based angle-resolved photoelectron spectroscopy. However, little is known about the associated unoccupied states, and control of the Fermi-level position across the band gap would be desirable. Intercalated silver presents a prototypical example where 2D quantum confinement and inversion symmetry breaking entail a metal-to-semiconductor transition. Intrinsically capped into a van der Waals heterostructure with overhead graphene, they compose a new class of quantum materials with striking properties contrasting their parent bulk crystals. Recently the graphene-SiC interface has emerged as a versatile platform for the epitaxy of otherwise unstable, monoelemental, two-dimensional (2D) layers via intercalation.
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