Abstract

The main physical reason why spintronics is promising for applications is that the lifetime of a carrier spin is much longer than the energy relaxation time. In other words, while orbital motion of a carrier at high temperature is completely incoherent, the carrier spin still “remembers” its initial direction. Due to this long lifetime, the response of the spin polarization to external fields, namely, dc-field, ac-drive, and random hyperfine field, can be studied experimentally even at room temperature. Theoretically, the spin dynamics in external fields is quite nontrivial. We studied the following delicate manifestations of this dynamics all related to experiments:
(i) Evolution of the spin noise spectrum with ac drive.
(ii) Spin-dependent resonant tunneling between normal and ferromagnetic electrodes.
(iii) Spin pumping from a ferromagnet into a hopping insulator.
(iv) The shape of the Hanle curves in transition metal dichalcogenides, possessing strong built-in spin-orbit fields.

Another peculiar aspect of the spin degree of freedom is that spin-orbit coupling can affect the motion of the spin fluxes (spin Hall effect) or even create spin-polarized edge states (quantum spin Hall effect). Both phenomena were observed experimentally. We studied the following aspects
of these phenomena:
(i) Quantum spin Hall effect in the presence of magnetic dopants which eliminate one of the two counter-propagating edge states (quantum anomalous Hall effect).
(ii) Effective spin Hall properties of a medium with strongly inhomogeneous spin-orbit coupling.