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The band edges of typical 2D semimetals and semiconductors are found at two corners of the first Brillouin zones, commonly referred to as K and K’ valleys. Efforts have been made in initiating valley-polarized current (valleytronics) for low-dissipation quantum electronics, akin to that of spintronics. In monolayer transition metal dichalcogenides, dynamic valley polarization can be achieved with optical excitations. At a 1D boundary of two bilayer graphene domains (natural or gate-defined), topological valley-chiral states can be realized by electrostatics alone. However, the demanding fabrication requirements limit device reproducibility and controllability, and therefore scalability towards larger scale valleytronics circuits with more advanced functionality. In this work, we develop a new device architecture of point junction that addresses these device limitations. A PN junction and a quantum point contact20,21 is simultaneously defined at the center of the device, where valley-chiral states can be easily configured and switched on/off with high device yield. With valley chirality tuned on/off, we characterize a valley polarization of ~80% at zero magnetic field. By eliminating unintended scattering centers, we demonstrate Shubnikov–de Haas (SdH) oscillation via valley-chiral modes under finite magnetic field, with ballistic dip resistances at expected quantization of 4e2/h. The easy-to-configure valley-chiral states provide a new platform to study valley-polarized quantum phenomena in graphene and paves a path towards scalable valleytronics.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Valleytronics, bilayer graphene, valley-polarized current

刊行年月日: 2024-09-13

出版者: American Association for the Advancement of Science (AAAS)

掲載誌:

• Science Advances (ISSN: 23752548) vol. 10 issue. 37 eadp6296

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1126/sciadv.adp6296

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更新時刻: 2025-02-23 22:46:21 +0900

MDRでの公開時刻: 2025-02-23 22:46:21 +0900