Quantum Control of Graphene Plasmon Excitation and Propagation at Heaviside Potential Steps.

Quantum mechanical effects of single particles can affect the collective plasmon behaviors substantially. In this work, the quantum control of plasmon excitation and propagation in graphene is demonstrated by adopting the variable quantum transmission of carriers at Heaviside potential steps as a tuning knob. First, the plasmon reflection is revealed to be tunable within a broad range by varying the ratio γ between the carrier energy and potential height, which originates from the quantum mechanical effect of carrier propagation at potential steps. Moreover, the plasmon excitation by free-space photos can be regulated from fully suppressed to fully launched in graphene potential wells also through adjusting γ, which defines the degrees of the carrier confinement in the potential wells. These discovered quantum plasmon effects offer a unified quantum-mechanical solution toward ultimate control of both plasmon launching and propagating, which are indispensable processes in building plasmon circuitry.

Quantum transmission through the n-p-n heterojunction of massive 8-Pmmnborophene.

We investigate the quantum transmission through the n-p-n heterojunction of massive 8-Pmmnborophene. It is found that the Dirac mass of the electron interacts nontrivially with the anisotropy of the 8-Pmmnborophene, leading to the occurrence of new transmission behaviors in this n-p-n heterojunction. Firstly, the effective energy range of nonzero transmission can be reduced but deviates from the mass amplitude, which induces the further controllability of the transmission property. Secondly, even if the equal-energy surfaces in the p and n parts do not encounter in thek-space, finite transmission is allowed to occur as well. In addition, the existence of Dirac mass can change the reflection manner from the retroreflection to the specular reflection under appropriate conditions. The findings in this work can be helpful in describing the quantum transport properties of the heterojunction based on 8-Pmmnborophene.

Theoretical study of nitrogen, boron, and co-doped (B, N) armchair graphene nanoribbons.

The electronic properties of the graphene nanoribbons (GNR) with armchair chirality were studied using the density functional theory (DFT) combined with non-equilibrium green's function method (NEGF) formalism. The role of donor and acceptor dopants of nitrogen and boron was studied separately and also in the situation of co-doping. The charge density, electronic density of states (DOS), and transmission coefficient at different bias voltages are presented for comparison between pure and doped states. It was found that this doping plays the main role in the distortion of the GNR lattices for cases of B and N as it affects straightly on the DOS and transmission coefficient of the systems under study. The band structure of edge was engineered by differently selecting the doping positions of B, N, and B-N hexagonal rings and it was found that there are significant changes in the electronic properties of these systems due to doping. This study can be used for developing GNR device based on doping B and N atoms.