Pedro Brandimarte

Crossed graphene nanoribbons as beam splitters and mirrors for electron quantum optics

Physical Review B - 2020    

Abstract

We analyze theoretically four-terminal electronic devices composed of two crossed graphene nanoribbons (GNRs) and show that they can function as beam splitters or mirrors. These features are identified for electrons in the low-energy region where a single valence or conduction band is present. Our modeling is based on p_z orbital tight binding with Slater-Koster-type matrix elements fitted to accurately reproduce the low-energy bands from density functional theory calculations. We analyze systematically all devices that can be constructed with either zigzag or armchair GNRs in AA and AB stackings. From Green’s function theory the elastic electron transport properties are quantified as a function of the ribbon width. We find that devices composed of relatively narrow zigzag GNRs and AA-stacked armchair GNRs are the most interesting candidates to realize electron beam splitters with a close to 50:50 ratio in the two outgoing terminals. Structures with wider ribbons instead provide electron mirrors, where the electron wave is mostly transferred into the outgoing terminal of the other ribbon, or electron filters where the scattering depends sensitively on the wavelength of the propagating electron. We also test the robustness of these transport properties against variations in the intersection angle, stacking pattern, lattice deformation (uniaxial strain), inter-GNR separation, and electrostatic potential differences between the layers. These generic features show that GNRs are interesting basic components to construct electronic quantum optical setups.

Press release

Bibtex citation

@Article{Sanz2020,
  author    = {Sofia Sanz and Pedro Brandimarte and G{\'{e}}za Giedke and Daniel S{\'{a}}nchez-Portal and Thomas Frederiksen},
  title     = {Crossed graphene nanoribbons as beam splitters and mirrors for electron quantum optics},
  journal   = {Physical Review B},
  year      = {2020},
  volume    = {102},
  number    = {3},
  pages     = {035436},
  doi       = {10.1103/physrevb.102.035436},
  publisher = {American Physical Society ({APS})},
}

Key words

• quantum transport
• electronic beam splitter
• graphene nanoribbons
• non-equilibrium Green's function
• tight-binding model