Nonlinear transport of ballistic Dirac electrons tunneling through a tunable potential barrier in graphene

TL;DR

This paper investigates nonlinear and tunneling transport of Dirac electrons in graphene with a tunable potential barrier, revealing control mechanisms for tunneling resistance and electron filtering useful for device applications.

Contribution

It introduces a numerical approach validated against analytical models to analyze nonlinear transport in graphene with a tunable barrier, including effects of energy gaps and bias fields.

Findings

Bias field controls tunneling resistance peaks.

Energy gap suppresses head-on and skew transmission.

Gapless graphene filters electrons outside normal incidence.

Abstract

Dirac-electronic tunneling and nonlinear transport properties with both finite and zero energy bandgap are investigated for graphene with a tilted potential barrier under a bias. For validation, results from a finite-difference based numerical approach, which is developed for calculating transmission and reflection coefficients with a dynamically-tunable (time-dependent bias field) barrier-potential profile, are compared with those of both an analytical model for a static square-potential barrier and a perturbation theory using Wentzel-Kramers-Brillouin (WKB) approximation. For a biased barrier, both transmission coefficient and tunneling resistance are computed and analyzed, indicating a full control of the peak in tunneling resistance by bias field for a tilted barrier, gate voltage for barrier height, and energy for incoming electrons. Moreover, a finite energy gap in graphene is found to suppress head-on transmission as well as skew transmission with a large transverse momentum. For a gapless graphene, on the other hand, filtering of Dirac electrons outside of normal incidence is found and can be used for designing electronic lenses. All these predicted attractive transport properties are expected extremely useful for the development of novel electronic and optical graphene-based devices.