Gate-Tunable Resonance State and Screening Effects for Proton-Like Atomic Charge in Graphene

Abstract

The ability to create a robust and well-defined artificial atomic charge in graphene and understand its carrier-dependent electronic properties represents an important goal toward the development of graphene-based quantum devices. Herein, we devise a new pathway toward the atomically precise embodiment of point charges into a graphene lattice by posterior (N) ion implantation into a back-gated graphene device. The N dopant behaves as an in-plane proton-like charge manifested by formation of the characteristic resonance state in the conduction band. Scanning tunneling spectroscopy measurements at varied charge carrier densities reveal a giant energetic renormalization of the resonance state up to 220 meV with respect to the Dirac point, accompanied by the observation of gate-tunable long-range screening effects close to individual N dopants. Joint density functional theory and tight-binding calculations with modified perturbation potential corroborate experimental findings and highlight the short-range character of N-induced perturbation.

Numerical package for QFT calculations of defect-induced phenomena in graphene

“…Figures 6(a) and (b), along with the results from [47] supports our hypothesis that the observed collapse in [22] is likely attributable to the increase of the cluster extent rather than the magnitude of the Coulomb potential.…”

“…We observe that as the potential becomes more negative (U ∼ 3 eV), a single bound state splits off from the bottom of the band (∼8.5 eV) and it drifts downwards as the consequence of increasingly attractive potential. The presence of the spectral pole is confirmed by DFT calculations for the nitrogen dopant [47]. A symmetrical effect can be seen for positive (repulsive) potential.…”

“…While it is unambiguous that the spectral function undergoes a critical transition as the cluster size goes from four to five, the nature of the potential produced by the artificial nucleus is less evident. A recent work [47] investigated nitrogen atoms embedded in graphene by replacing individual carbon atoms. Using a combination of experimental data, DFT, and tight-binding parameterization, it was determined that the potential produced by the additional proton of the nitrogen nucleus is fairly short-ranged.…”

Performance benchmarking of an ultra-low vibration laboratory to host a commercial millikelvin scanning tunnelling microscope

“…More so, such capability would allow multiple electrodes to be integrated to contact and control a micron-sized electrical device, e.g. by application of gate voltages [29,[42][43][44][45][46][47][48]. As access with long focal optical microscopes [29] is not easily possible in the DR environment, here, we employ a capacitance-mediated approach [49] for landing the STM tip onto a micron-sized sample.…”

Atomic Valley Filter Effect Induced by an Individual Flower Defect in Graphene

“…[1][2][3] Previous studies have been demonstrated that single-atom defects in graphene, including an individual C-atom vacancy, H-atom absorption, and N-atom substitution, can efficiently break the local sublattice symmetry of graphene, and hence, give rise to valley-polarized states. [4,5] Topological defects are another kind of atomic defects that are usually ubiquitous and unavoidable in graphene during the epitaxial growth. [6] For each topological defect, the local hexagonal lattice prefers to reconstruct into networks of five-and seven-membered rings, nesting in the intrinsic graphene lattice and leaving no unsatisfied bonds.…”