Spin-orbit coupling means the system has a non-collinear spin. Therefore, spin exists as a spinor, hence there is no meaning to 'up' and 'down' spin. Still, is there any way to get fat-band plot separating 'up' and 'down' spin for a system with SOC?
- Xu, X.; Ma, Y.; Zhang, T.; Lei, C.; Huang, B.; Dai, Y. Nonmetal-Atom-Doping-Induced Valley Polarization in Single-Layer Tl2O. J. Phys. Chem. Lett. 2019, 10 (16), 4535–4541. DOI: 10.1021/acs.jpclett.9b01602.