Tunable Superlattice in Graphene To Control the Number of Dirac Points

Abstract

Superlattice in graphene generates extra Dirac points in the band structure and their number depends on the superlattice potential strength. Here, we have created a lateral superlattice in a graphene device with a tunable barrier height using a combination of two gates. In this Letter, we demonstrate the use of lateral superlattice to modify the band structure of graphene leading to the emergence of new Dirac cones. This controlled modification of the band structure persists up to 100 K.

Towards superlattices: Lateral bipolar multibarriers in graphene

“…This stands in contrast to the argumentation of Ref. [28], where a similar device with an even higher number of top gate stripes was investigated. Our calculations for a fully phase coherent system of N TG top gate stripes yield growing of resistance peaks due to the formation of new touching points of valence and conductance band as the band structure gets folded, giving rise to the opening of small energy band gaps.…”

“…We focus our research on locally gated graphene with varying number of bipolar barriers and different spacing in order to characterize the impact of changing parameters on the resistance of the monolayer. A recent publication on a similar lateral multibarrier setup [28] attributes the occurring resonant behavior of the resistance in the bipolar regime to a superlattice effect in the lowdiffusive limit, even though the experimental elastic mean free path does not exceed one lattice period. We reproduce the reported resonant features and provide extended data for varying experimental parameters that can be explained within a consistent Fabry-Pérot resonance model, without resorting to a superlattice effect.…”

Tuning equilibration of quantum Hall edge states in graphene – Role of crossed electric and magnetic fields

“…The ability to create abrupt (∼ 10 nm) tunable barriers in graphene allows new aspects to be explored. In addition, new physics, due to the role of crossed electric and magnetic field, that cannot be seen in conventional 2DEGS can be studied in SL structures based on graphene.In this letter, we study magneto transport in an electrostatically defined 1D lateral SL in graphene [13]. In our device we apply a perpendicular magnetic field and periodically modulate the charge carrier density in adjacent "ribbons" of graphene, tuning from an array of p-p' (or n-n' ) to an array of p-n' junctions.…”

“…The geometric width of each top-gates is ∼ 30 nm and they have a period of λ = 150 nm. The effective electrostatic width of the top-gates felt by the charge carriers in graphene is larger due to the finite thickness of the top-gate dielectric [13] (details in Section VII of Supplemental Material).In our device, graphene consists of two alternating regions -one where the charge carrier density is controlled only by the back-gate (BG region); and the other where the charge carrier density is controlled by both the topgate and the back-gate (TG region). The difference in charge carrier density between BG and TG regions gives rise to a SL whose amplitude (V 0 ) is controlled by V bg and…”

“…|CtgVtg+C bg V bg | e ) [13], where V tg (V bg ) is the topgate (back-gate) voltage, C tg (C bg ) is the capacitance per unit area of top-gate (back-gate), e is the electronic charge and v F is the Fermi velocity.) (Details of calcuarXiv:1504.04952v2 [cond-mat.mes-hall]…”