title: Quantum mechanical interpretation of the ultrafast all optical spin switching.
abstract: The all-optical spin switching induced by an intense (∼TW cm-2), near-infrared (775 nm), ultrashort (∼100 fs) circularly-polarized laser pulse is studied based on the spin-orbit coupled Heisenberg model. We find that the magnetic spin momentum undergoes an oscillation in time during the interaction with a driving laser pulse, which can be explained as a classical counterpart of the Rabi oscillation associated with a spin-orbit coupling. The optimal spin reversal is achieved by adjusting the pulse duration to one half the Rabi oscillation period. A successive spin reversal by a delayed pulse is possible if it has the opposite helicity and a shorter duration relative to the first pulse. Moreover, inclusion of an exchange interaction term in the Hamiltonian leads to a precession of the magnetic spin momentum that lasts even after the driving laser pulse turns off. This spin precession is stronger in antiferromagnets than ferrimagnets.
authors.affiliation: Department of Physics, Indiana State University, Terre Haute, IN 47809, United States of America.
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Murakami
authors.forename: Zach
authors.initials: Z
authors.lastname: Babyak
authors.forename: Michael
authors.initials: M
authors.lastname: Giocolo
authors.forename: G P
authors.initials: GP
authors.lastname: Zhang