Minimally twisted bilayer graphene with interlayer potential asymmetry hosts one-dimensional topological helical states at domain walls between AB/BA-stacking regions. However, the nature of topological helical states' propagation remains elusive. Although it is widely believed that they form a two-dimensional triangular network, a few argue that they self-organize into one-dimensional topological zigzag modes that propagate independently. In this Letter, we propose a protocol based on a two-terminal twisted bilayer graphene 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 topological helical states indeed self-construct the one-dimensional distorted topological zigzag modes, each bypassing the AA-stacking spots and propagating independently. By considering a long twisted bilayer graphene 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 topological zigzag modes. Our work not only clarifies the propagation nature of the topological helical states, but also realizes an array of one-dimensional conducting channels on a two-dimensional platform. This work provides a way of engineering topological states intrinsic in twisted bilayer graphene.

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• Ballistic transport
• Edge states
• Electrical conductivity
• Twistronics
• Valley degrees of freedom
• Graphene
• Twisted bilayer graphene
• Band structure methods
• Nonequilibrium Green's function
• Tight-binding model