Physical Origin of Current Partition at a Topological Trifurcation

TL;DR

This paper investigates the microscopic mechanisms behind current partitioning at topological trifurcations in twisted bilayer graphene, revealing a 'bypass jump' process that explains counterintuitive transport behavior.

Contribution

It introduces a wavepacket dynamics method to analyze electronic transport at topological intersections in twisted bilayer graphene, providing new insights into current partitioning mechanisms.

Findings

Counterintuitive current partitioning explained by 'bypass jump' mechanism

Wavepacket dynamics accurately reproduce transport properties

Topological trifurcation naturally arises in minimally twisted bilayer graphene

Abstract

In gated bilayer graphene, topological zero-line modes (ZLMs) appear along lines separating regions with opposite valley Hall topologies. Although it is experimentally difficult to design the electric gates to realize ZLMs due to the extremely challenging techniques, twisted bilayer graphene provides a natural platform to produce ZLMs in the presence of uniform electric field. In this Letter, we develop a set of wavepacket dynamics, which can be utilized to characterize various gapless edge modes and can quantitatively reproduce the electronic transport properties at topological intersections. To our surprise, in the minimally twisted bilayer graphene where a topological trifurcation intersection naturally arises, we show that the counterintuitive current partition (i.e., the direct transport propagation) originates from the microscopic mechanism "bypass jump". Our method can be applied to understand the microscopic pictures of the electronic transport features of all kinds of topological states.