3.

(a) Schematic of the electron QPC in the WSe₂/BLG heterostructure. (b) Single-particle band structure of a 30 nm wide QPC on BLG/WSe₂, calculated using the DFT SOC parameters from ref . (c) Bias spectroscopy of the QPC at B = 0 and T = 1.3 K. The alternating white diamond-shaped regions correspond to conductance plateaus, with values indicated in units of e ²/h. (d) High-resolution bias spectroscopy of the first G = 2e ²/h plateau, measured at 10 mK. The diamond height directly yields 2Δ_SO. (e) Transconductance dG/dV _CG as a function of V _CG and B _⊥, measured at T = 1.3 K. Black labels indicate corresponding conductance quantum numbers. (f) Calculated single-particle magnetic subband evolution for a 30 nm wide QPC in BLG/WSe₂, showing excellent agreement with the experimental data across both low and high magnetic fields. The characteristic “3 + 1” feature, resulting from spin–valleyZeeman coupling, is highlighted with the magenta circle. The magenta arrow marks the crossing between the 1K^– ↑ – 3K⁺ ↓ states, in panels e and f. This “3 + 1” feature is discussed more in detail in SI Section E6.