Fig. 1: General information of 2M-WS2.
a Schematic illustration of the crystal structure of 2M-WS2. Only the framework of W atoms is shown. The inset shows the building block structure of [WS6]8-. The boundaries of the primitive and conventional unit cells are indicated by magenta and blue lines, respectively. b Bulk Brillouin zone (BZ) marked with eight time-reversal-invariant momenta. The red rectangle plane indicates the 2D BZ of the (100) natural cleavage surface. c Schematic phase diagram as a function of temperature and magnetic field21. d Schematic phase diagram as a function of carrier concentration and temperature24. \({T}_{{\rm{C}}}^{{\rm{opt.}}}\) is the optimal superconducting transition temperature. e First-principles calculated phonon dispersions. The magenta and blue dots mark the Raman active Ag and Bg modes, respectively. f Raman spectra measured at 5 K in circularly co-polarization (LL) and cross-polarization (LR) configurations, respectively. LL (LR): the first letter represents the polarized state of excited light, whereas the second letter represents the polarized state of scattering Raman signal. L and R denote left-handed and right-handed circularly polarized light, respectively. g Left panel: first-principles calculated (100)-surface-projected noninteracting band structure. The topological surface states (TSSs) are appended with red lines. The white arrows indicate the saddle-like bands near EF. Right panel: The total noninteracting bulk density of states (DOS) peaks at EF with the peak value of 1.38 states/eV/f.u. (f.u. represents formula unit).
