Tunneling conductivity fast modulated by optically-dressed electrons in graphene and a dice lattice

TL;DR

This paper investigates how a linearly-polarized off-resonant dressing field modulates tunneling current and conductivity in graphene and dice lattices, revealing significant laser-induced enhancements useful for ultrafast optoelectronic devices.

Contribution

It introduces a novel analysis of laser-dressing effects on tunneling in graphene and dice lattices, highlighting anisotropic energy dispersion and asymmetric Klein-paradox phenomena.

Findings

Laser dressing induces anisotropy in electron energy dispersion.

Significant enhancement of tunneling conductivity with increased laser intensity.

Asymmetric Klein-paradox observed for off-normal tunneling directions.

Abstract

Based on the transmission coefficient of tunneling electrons, we have presented tunneling current and conductivity across a square-potential barrier for both graphene and $\alpha$-$\mathcal{T}_3$ lattices under a linearly-polarized off-resonant dressing field. The presence of such a dressing field introduces an anisotropy factor in the energy dispersion of tunneling electrons so that the cross section of a Dirac-cone appears as elliptical. Consequently, the field-polarization controlled major axis of the ellipse will be misaligned with the normal direction of a barrier layer in the tunneling system, which exhibits an asymmetric Klein-paradox for an off-normal-direction tunneling. The resulting tunneling current in this system is calculated by using a transmission coefficient and a longitudinal group velocity (different from a longitudinal momentum) of electrons. By presenting numerically calculated tunneling conductivity modified by a laser dressing field, we demonstrate a significant enhancement of electrical conductivity by external laser-field intensity, which is expected to be crucial in application of ultrafast optical modulation of opto-electronic devices for photo-detection and fiber-optic communication.