Topological surface state enhanced ultrafast spin dynamics of Fe/Bi(2)Se(3 )heterostructures

Topological insulators (TIs) with distinct topological surface states (TSSs) have served as fertile ground to investigate spintronics and quantum information devices. Spin transport properties of ferromagnet (FM)/TI heterostructures have been revealed due to the spin-momentum-locked TSS. The role of the TSS on laser-induced ultrafast spin dynamics, however, is not well understood. Here, we find that the TSS can not only significantly accelerate the ultrafast demagnetization but can also enhance the Gilbert damping factor of Fe/Bi2Se3 heterostructures. We conclude that the TSS enhanced ultrafast spin dynamics is attributed to the strong hybridization of Fe and Bi2Se3 orbitals near the Fermi level. Our findings suggest that the manipulation of ultrafast spin dynamics of a FM/TI via the TSS can open an avenue to utilize future topological spintronic devices or quantum information processing approaching femtosecond timescales.