Weak Localization and Transport Gap in Graphene Antidot Lattices

TL;DR

This study investigates how antidot lattice geometry in graphene influences quantum effects, revealing size-dependent quantum Hall behavior, transport gaps, and weak localization phenomena.

Contribution

It demonstrates the fabrication of graphene antidot lattices with tunable properties and analyzes their quantum transport characteristics, highlighting size and edge effects.

Findings

Quantum Hall effect diminishes with smaller antidot spacing.

Narrow constrictions create high-resistance states and transport gaps.

Pronounced weak localization indicates strong intervalley scattering.

Abstract

We fabricated and measured antidot lattices in single layer graphene with lattice periods down to 90 nm. In large-period lattices, a well-defined quantum Hall effect is observed. Going to smaller antidot spacings the quantum Hall effect gradually disappears, following a geometric size effect. Lattices with narrow constrictions between the antidots behave as networks of nanoribbons, showing a high-resistance state and a transport gap of a few mV around the Dirac point. We observe pronounced weak localization in the magnetoresistance, indicating strong intervalley scattering at the antidot edges. The area of phase-coherent paths is bounded by the unit cell size at low temperatures, so each unit cell of the lattice acts as a ballistic cavity.