Phase Coherent Transport in Graphene Nanoribbons and Graphene Nanoribbon Arrays

TL;DR

This study investigates quantum interference effects in graphene nanoribbons at very low temperatures, revealing phase coherence behavior and extending theoretical models to better understand electron transport.

Contribution

It provides experimental measurements of phase coherence length in graphene nanoribbons and extends the 1D weak localization theory to include all elastic scattering rates.

Findings

Phase coherence length saturates at low temperatures, exceeding ribbon width.

UCFs can be suppressed by averaging techniques to reveal WL.

Extended model describes weak localization at elevated temperatures.

Abstract

We have experimentally investigated quantum interference corrections to the conductivity of graphene nanoribbons at temperatures down to 20 mK studying both weak localization (WL) and universal conductance fluctuations (UCF). Since in individual nanoribbons at millikelvin temperatures the UCFs strongly mask the weak localization feature we employ both gate averaging and ensemble averaging to suppress the UCFs. This allows us to extract the phase coherence length from both WL and UCF at all temperatures. Above 1 K, the phase coherence length is suppressed due to Nyquist scattering whereas at low temperatures we observe a saturation of the phase coherence length at a few hundred nanometers, which exceeds the ribbon width, but stays below values typically found in bulk graphene. To better describe the experiments at elevated temperatures, we extend the formula for 1D weak localization in graphene, which was derived in the limit of strong intervalley scattering, to include all elastic scattering rates.