Download file (3.82 MB)
Download as zip (3.78 MB)

Collection

Citation

Description:

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.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Valleytronics, bilayer graphene, valley-polarized current

Date published: 2024-09-13

Publisher: American Association for the Advancement of Science (AAAS)

Journal:

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

Funding:

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1126/sciadv.adp6296

Related item:

Other identifier(s):

Contact agent:

Updated at: 2025-02-23 22:46:21 +0900

Published on MDR: 2025-02-23 22:46:21 +0900