Misalignment-robust zigzag gate geometry for valley filtering with helical point contacts

Resumo

Many experimental works reported the generation of valley-polarized currents in two-dimensional materials. However, most efforts require the application of external magnetic fields. Gate-defined valley-helical narrow channels offer a magnetic field-free approach to generate valley currents. However, achieving perfect helical transport in such gate-defined devices remains challenging due to stringent requirements for gate alignment. Misalignments lead to the presence of non-helical states that suppress the efficiency of these devices. Here, we propose an alternative gate layout to overcome the fabrication challenges. Our layout creates a series of helical quantum point contacts that suppress the transmission of non-helical modes. We show that such a layout can be implemented with four layers of independent gates or two layers of split gates. Thus, our approach offers a robust magnetic field-free platform to generate valley-polarized currents.