Interchannel coupling induced gapless modes in multichannel zero-line systems

In bilayer graphene, the application of a perpendicular electric field breaks the inversion symmetry to open a bulk band gap to harbor the quantum valley Hall effect. When the field varies spatially, a topologically confined mode (also named the zero-line mode) arises along the zero-field line. In this work, we theoretically investigate the electronic transport properties of the multichannel zero-line systems. The finite-size effect in topological systems (e.g., quantum Hall effect, topological insulators) often induces a topologically trivial gap to realize a normal insulator. To our surprise, we find that the coupling between neighboring zero lines can give rise to striking electronic properties depending on the number of channels m, i.e., a trivial band gap for even m, whereas a nontrivial gapless mode for odd m. We further show that these findings apply to various ribbon orientations. A general effective model is constructed to provide a clear physical picture of the emergence of gapless modes. In the end, a gate-tunable device is proposed to function as a switch with controllable current partitions. We believe that our findings are experimentally accessible, and have potential practical applications in designing multifunctional valley-based electronics.

Automated summary

In this work, the authors theoretically investigate the electronic transport properties of multichannel zero-line systems in bilayer graphene. They find that the coupling between neighboring zero lines can result in different electronic properties, depending on the number of channels. These findings have potential applications in designing multifunctional valley-based electronics.