Current development of noncollinear electronic structure theory

In this Perspective, we review recent developments in noncollinear electronic structure theory. After a brief historical overview of studies into broken symmetry wave functions, we show that noncollinear wave functions are necessary for studying spin and magnetic phenomena on account of spin-symmetry breaking terms in the Hamiltonian. Recent developments applying noncollinear electronic structure theory to magnetization dynamics, spin dynamics, and spin-orbit coupling in excited state properties are showcased. We also discuss some recent developments in noncollinear density functional theory. Finally, we comment on the future of noncollinear electronic structure theory.