17 research outputs found
Approaching the Intrinsic Bandgap in Suspended High-Mobility Graphene Nanoribbons
We report electrical transport measurements on a suspended ultra-low-disorder
graphene nanoribbon(GNR) with nearly atomically smooth edges that reveal a high
mobility exceeding 3000 cm2 V-1 s-1 and an intrinsic band gap. The
experimentally derived bandgap is in quantitative agreement with the results of
our electronic-structure calculations on chiral GNRs with comparable width
taking into account the electron-electron interactions, indicating that the
origin of the bandgap in non-armchair GNRs is partially due to the magnetic
zigzag edges.Comment: 22 pages, 6 figure
Surface Dynamics and Ligand−Core Interactions of Quantum Sized Photoluminescent Gold Nanoclusters
Quantum-sized metallic clusters protected by
biological ligands represent a new class of luminescent materials;
yet the understanding of structural information and photoluminescence origin of these ultrasmall clusters remains a
challenge. Herein we systematically study the surface ligand
dynamics and ligand−metal core interactions of peptide-protected
gold nanoclusters (AuNCs) with combined experimental
characterizations and theoretical molecular simulations. We
show that the peptide sequence plays an important role in
determining the surface peptide structuring, interfacial water
dynamics and ligand−Au core interaction, which can be tailored
by controlling peptide acetylation, constituent amino acid electron donating/withdrawing capacity, aromaticity/hydrophobicity
and by adjusting environmental pH. Specifically, emission enhancement is achieved through increasing the electron density of
surface ligands in proximity to the Au core, discouraging photoinduced quenching, and by reducing the amount of surfacebound water molecules. These findings provide key design principles for understanding the surface dynamics of peptideprotected nanoparticles and maximizing the photoluminescence of metallic clusters through the exploitation of biologically
relevant ligand properties
Experimental discovery of a topological Weyl semimetal state in TaP
[[abstract]]Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal’s surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission.[[notice]]補æ£å®Œ