Figure 2

(a) Crossings between the E-like \(\varvec{k}=0\) subband edges and the H-like subbands as a function of \(d_0\), and \(t=3\) nm (All the subbands are spin-degenerate). (b) Phase diagram as a function of \(d_0\) and t. The black solid lines mark the E–H subband crossings, and the red circles along the \(t=3\) nm line correspond to those in (a). Shaded region marks the SM phase, and the colors within phases I and II refer to hybridization gap between H subbands, \(\Delta E_H\), which becomes clear only for \(t < 1\) nm, and also splits the first solid black line for the \(E_1^-\)–\(H_1\) crossings. The cyan stars along the \(t=3\) nm line mark the points (0, I, II, III) corresponding to the phases illustrated in Fig. 1b–e. The shaded rectangle near \(d_0 = 6.7\) nm and \(t=3\) nm marks the parameters of the experimental sample, with the area shaped to illustrate the experimental uncertainty of \(\pm 0.3\) nm in both \(d_0\) and t.