Relativistic effects at surfaces and interfaces

The atomic spin–orbit coupling (SOC) is a relativistic phenomenon for electrons moving around a nucleus. SOC couples the spin and orbital motions of freedom of an electron. SOC also gives rise to a significant effects on low-dimensional systems such as solid surfaces and interfaces, where the structural inversion symmetry is broken, yielding non-trivial phenomena such as the spin splitting of two-dimensional electronic energy bands without an external magnetic field. SOC also creates an unusual state of matter, topological insulator. In this short review, strong spin–orbit coupling and its consequences at surfaces and interfaces are briefed.