Extended Data Fig. 2: Device structures for aligned T_d-WTe₂/monolayer H-WSe₂ devices.

a, schematics of an angle-aligned monolayer WTe₂/monolayer WSe₂ device. Top: cross-section of the device. A thin hBN spacer is inserted between the WTe₂ and the platinum (Pt) electrodes to avoid direct edge contacts. Gr stands for few-layer graphite gate electrode. Bottom: top view of the device. The blue and red lines denote the helical edge states of a quantum spin Hall insulator. The measurement configuration is also shown. b, optical image of a typical angle-aligned monolayer WTe₂/ monolayer WSe₂ device. Red, blue and black dashed lines mark the WSe₂, the WTe_2, and the hBN spacer flakes, separately. c, optical image of the a typical angle-aligned bilayer WTe₂/ monolayer WSe₂ device. Red and blue dashed lines mark the WSe₂ and the bilayer WTe₂ flakes, separately.