Extended Data Fig. 4: E_z-dependent Rashba splitting energy E_SO of the D^± and Γ valleys in QL BAs.

The DFT-calculated E_SO of the D^± valleys is larger than that of the Γ Rashba valleys within the whole E_z range. Using the LK formula fitting (Supplementary Note 9), we can also deduce experimental E_SO from V_g-dependent SdHOs, as shown by the black curve. Although DFT overestimates E_SO by a factor of two, it is clear that both DFT and experimental results show the same trend in the linear growth of E_SO as a function of E_z. Equally important, both results prove that E_SO is substantial enough to be probed by quantum transport below liquid helium temperature. Note that E_z is calculated by interfacial Gauss’s law (Supplementary Note 6).