Abstract
We have investigated electron tunneling through an atomically smooth square potential barrier for both the dice lattice and graphene under a linearly polarized off-resonant and high-frequency dressing field. We have demonstrated Klein tunneling for a nonzero angle of incidence which is due to a nonalignment of optically controllable elliptical energy dispersions for the dressed states of Dirac particles and the direction of incoming kinetic particles. This finite angle of incidence has been found to depend on the light-induced anisotropy of energy dispersion, which is a function of the electron-light coupling strength, as well as the misalignment between directions of the light polarization and the electron beam incident on the potential barrier. Additionally, we have discovered much larger off-peak transmission amplitudes for dice lattices in contrast to graphene. We anticipate that the theoretical predictions could be applied to a wide range of Dirac materials and exploited for controlling both coherent tunneling and ballistic transport of electrons in the construction of novel electronic, optical, and valleytronic nanoscale switching devices.3 MoreReceived 27 June 2020Accepted 19 October 2020DOI:https://doi.org/10.1103/PhysRevResearch.2.043245Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBallistic transportCarrier dynamicsElectrical conductivityElectronic structureOptoelectronicsCondensed Matter, Materials & Applied Physics
Highlights
The α − T3 model is one of the most recent and a very promising system with zero-mass Dirac fermions [1]
Even though this paper focuses on two opposite limits for graphene with α = 0 as well as dice lattice with α = 1, we still present relevant discussions on properties pertaining to the general α − T3 model
For both graphene and dice lattice, linearly polarized irradiation creates anisotropy between in-plane components of the electron wave vector and modifies the phase factors of individual wavefunction components, while magnitudes for the components of wave functions remain unchanged. Such light-induced modifications of material properties are found to be quite different for graphene and dice lattice mainly due to the presence of the flat band in the energy dispersions of the dice
Summary
The α − T3 model is one of the most recent and a very promising system with zero-mass Dirac fermions [1]. The resulting energy dispersion is distinguished by the presence of a completely flat band with infinite degeneracy exactly at the Dirac point, and acquires a Dirac cone structure as in graphene simultaneously. The lattice structure for the α − T3 model consists of a honeycomb lattice of atoms plus an additional hub atom at the center of each hexagon This hub atom couples to one of the A- or B-sublattice atoms on the rim with its hopping coefficient equal to a fraction of that between two neighboring sublattice atoms on the hexagon rim sites. This ratio α varies from 0, which is equivalent to the model for graphene with a completely decoupled set of hub atoms, to 1, corresponding to a dice lattice in which the influence of the extra hub atom reaches a maximum
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