Fig. 4: Spin textures of the (100) surface states of Bi4Br4.

a, b Calculated z′- and x′-component of spin polarization of the (100) surface states. c, d Calculated spin textures of the (100) surface states at the energy positions marked by the arrows in a. e, f Experimental z′- and x′-component of spin polarization of the (100) surface states. g, h z′-component of spin-resolved momentum distribution curves (MDCs) and corresponding spin polarization at selected binding energies marked by the dashed lines in e. Data were collected using a 7-eV laser at 140 K.