Transport Anisotropy in One-dimensional Graphene Superlattice in the High Kronig-Penney Potential Limit

TL;DR

This study demonstrates high Kronig-Penney potential modulation in one-dimensional graphene superlattices using nanoscale ferroelectric gating, revealing anisotropic electronic properties and satellite Dirac points.

Contribution

It introduces a method to achieve high KP potential in graphene via ferroelectric domain gating, enabling exploration of electron supercollimation and flat band phenomena.

Findings

Satellite Dirac points scale with superlattice period as L^(-1.18)

Fermi velocity perpendicular to superlattice is quenched to about 1%

High KP potential scenario explains observed band reconstruction

Abstract

One-dimensional graphene superlattice subjected to strong Kronig-Penney (KP) potential is promising for achieving electron lensing effect, while previous studies utilizing the modulated dielectric gates can only yield a moderate, spatially dispersed potential profile. Here, we realize high KP potential modulation of graphene via nanoscale ferroelectric domain gating. Graphene transistors are fabricated on PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$ back-gates patterned with periodic, 100-200 nm wide stripe domains. Due to band reconstruction, the h-BN top-gating induces satellite Dirac points in samples with current along the superlattice vector $\hat{s}$, a feature absent in samples with current perpendicular to $\hat{s}$. The satellite Dirac point position scales with the superlattice period ($L$) as $\propto L^{\beta}$, with $\beta = -1.18 \pm 0.06$. These results can be well explained by the high KP potential scenario, with the Fermi velocity perpendicular to $\hat{s}$ quenched to about 1% of that for pristine graphene. Our study presents a promising material platform for realizing electron supercollimation and investigating flat band phenomena.