摘要： Spintronics is the key word to motivate studies of spin-polarized electronic states in solids and at surfaces or interfaces. The use of the electron spin in addition to the electron charge as information carrier—that is the goal for spintronics devices. The generation, manipulation, and detection of spin-polarized currents promise applications in information technology. However, in many materials, the electronic states are spin degenerate. The spin degeneracy may be lifted by two interactions: (i) exchange interaction in magnetically ordered materials, where the magnetization direction is the reference for the alignment of the spin magnetic moments. Independent of location and momentum, the electron spin magnetic moment is either aligned parallel to the magnetization direction (majority spin, lower in energy) or antiparallel to it (minority, higher in energy), leading to a spin-dependent energy splitting, called exchange splitting, of the bands; (ii) spin–orbit interaction (SOI), which is present in all materials but becomes relevant in systems with high atomic number. In ferromagnets, SOI enables hybridization between bands of different spin character, leading to spin–orbit-induced energy gaps, sometimes called spin hot spots in the band structure, which are held responsible for demagnetization processes. Furthermore, noncollinear magnetic structures such as skyrmions arise from SOI in ferromagnets. In nonferromagnets, SOI leads to energy splitting of bands with different total angular momentum j but not necessarily to spin-split bands. Only in systems, where inversion symmetry is broken, which is, for example, the case at surfaces, the bands exhibit a spin-dependent energy splitting, which itself depends on the momentum k. This so-called Rashba-type spin splitting was predicted for a two-dimensional electron gas and experimentally observed in surface states on heavy metal surfaces, for example, Au(111) and W(110). The spin-dependent splitting depends on the momentum parallel to the surface kk and reverses its sign upon a sign change of kk. As a consequence, no net magnetic moment is formed. In contrast to Rashba systems, where surface states become spin split by SOI, topological insulators such as Bi2Se3 exhibit so-called topological surface states (TSS), which only appear as a consequence of SOI. SOI is responsible for band inversion and formation of a gap, which is then closed by a surface state with Dirac-cone-like energy dispersion and characteristic spin texture.