This review focuses on the chirality observed in the excited states of the
magnetic order, dielectrics, and conductors that hold transverse spins when
they are evanescent. Even without any relativistic effect, the transverse spin
of the evanescent waves are locked to the momentum and the surface normal of
their propagation plane. This chirality thereby acts as a generalized
spin-orbit interaction, which leads to the discovery of various chiral
interactions between magnetic, phononic, electronic, photonic, and plasmonic
excitations in spintronics that mediate the excitation of quasiparticles into a
single direction, leading to phenomena such as chiral spin and phonon pumping,
chiral spin Seebeck, spin skin, magnonic trap, magnon Doppler, and spin diode
effects. Intriguing analogies with electric counterparts in the nano-optics and
plasmonics exist. After a brief review of the concepts of chirality that
characterize the ground state chiral magnetic textures and chirally coupled
magnets in spintronics, we turn to the chiral phenomena of excited states. We
present a unified electrodynamic picture for dynamical chirality in spintronics
in terms of generalized spin-orbit interaction and compare it with that in
nano-optics and plasmonics. Based on the general theory, we subsequently review
the theoretical progress and experimental evidence of chiral interaction, as
well as the near-field transfer of the transverse spins, between various
excitations in magnetic, photonic, electronic and phononic nanostructures at
GHz time scales. We provide a perspective for future research before concluding
this article.Comment: 136 pages, 60 figure