Phosphorene pnp junctions as perfect electron waveguides

Abstract

The current flow in phosphorene pnp junctions is studied. At the interfaces of the junction, omnidirectional total reflection takes place, named anti-super-Klein tunneling, as this effect is not due to an energetically forbidden region but due to pseudo-spin blocking. The anti-super-Klein tunneling confines electrons within the junction, which thus represents a perfect lossless electron waveguide. Calculating the current flow by applying the Green's function method onto a tight-binding model of phosphorene, it is observed that narrow electron beams propagate in these waveguides like light beams in optical fibers. The perfect guiding is found for all steering angles of the electron beam as the total reflection does not rely on the existence of a critical angle. For low electron energies and narrow junctions, the guided modes of the waveguide are observed. The waveguide operates without any loss only for a specific orientation of the junction. For arbitrary orientations, minor leakage currents are found, which however decay for low electron energies and grazing incidence angles. It is shown that a crossroad shaped pnp junction can be used to split and direct the current flow in phosphorene. The proposed device, a phosphorene pnp junction as a lossless electron waveguide, may not only find applications in nanoelectronics but also in quantum information technology.

Gradient-index electron optics in graphene pn junctions

“…The possibility to manipulate electron beams in graphene by means of pn junctions or elastic deformations has lead to various proposals for nano-electronic devices, such as Veselago lenses [4,6,[29][30][31][32][33][34][35], electron fiber optics [3,36], interferometers [37,38], valley beam splitters [7,26,[39][40][41][42][43][44][45][46][47][48][49][50], collimators [51,52], switches [53], reflectors [54,55], transistors [2,56,57], and Dirac fermions microscopes [58]. Electron optics has been extended recently from graphene to other materials, such as phosphorene where negative reflection has been pre-dicted [59,60], non-coplanar refraction and Veselago lenses in Weyl semi-metals [61][62][63][64], anomalous caustics in borophene pn junctions [65], and super-diverging lenses in Dirac materials [30].…”