Theory of angular momentum transport

Transport in condensed matter physics is conventionally refers to charge and heat current. In spintronics, it is the angular momentum (AM) that delivers information from place to place. The AM propagation, or AM current, has three distinct forms known as the electron spin current, the incoherent magnon current and the coherent macroscopic magnon current. The conversion among these angular momentum currents lead to a number of spin transport phenomena including spin transfer torques, spin pumping, spin Hall and magnon drag. We present a unified theory to correlate these different angular momentum currents in magnetic multilayered structures by using semi-classical approaches for electrons and magnons. The formalism is applied to various multilayered systems and a few predictions are presented.