Arrays of one-dimensional conducting channels in minimally twisted bilayer graphene

TL;DR

This paper demonstrates that topological helical states in minimally twisted bilayer graphene self-organize into independent 1D zigzag modes, enabling arrays of 1D conducting channels on a 2D platform, confirmed by conductance quantization.

Contribution

It introduces a protocol to resolve the propagation nature of topological helical states, revealing their self-organization into 1D zigzag modes in TBG.

Findings

Nearly quantized conductance plateaus close to 1, 2, and 3 (in units of 2e^2/h)

Topological helical states form independent 1D zigzag modes

Array of 1D conducting channels realized in TBG

Abstract

Minimally twisted bilayer graphene (TBG) with interlayer potential asymmetry host one-dimensional (1D) topological helical states (THSs) at domain walls between AB/BA stacking regions. However, the nature of THS propagation remains elusive. Although it is widely believed that they form a two-dimensional (2D) triangular network, a few argue that they self-organize into 1D topological zigzag modes (TZMs) that propagate independently. In this Letter, we propose a protocol based on a two-terminal TBG nanoflake transport device and resolve this issue. Through rigorous calculations on the differential conductance and the nonequilibrium local density of states, we show that, these THSs indeed self-construct the 1D distorted TZMs, each bypassing the AA-stacking spots and propagating independently. By considering a long TBG nanoflake, we obtain a nearly quantized conductance plateau with its value close to 1, 2, and 3 (in units of $2e^2/h$), which serves as a strong experimental sign for the existence of TZMs. Our work not only clarifies the propagation nature of the THSs, but also realizes an array of 1D conducting channels on a 2D platform. This work provides an unprecedented way to engineering topological states intrinsic in TBG.