Eryin Wang

PtTe crystallizes in the CdI -type trigonal (1?T) structure with P m1 space group (No. 162). The crystal structure is composed of edge-shared PtTe octahedra with PtTe layers tiling the ab plane (Fig. 1c, d). The isostructural PtSe film with one monolayer thickness is a semiconductor with a 1.2?eV gap25 and exhibits helical spin texture with spin-layer locking26.

Although it is tempting to attribute the observed helical spin texture to R-1 Rashba effect induced by the structural asymmetry from the Pt substrate, further analysis, however, shows that this mechanism cannot explain our observations. For energy bands with the R-1 effect, there are two key features as follows: (1) two spin states are split at finite momenta and become degenerate at the ? point due to the time-reversal symmetry (Fig.