Single-Shot Helicity-Independent All-Optical Switching in Co/Ho Multilayers

Single-shot all-optical helicity-independent switching is established in $\mathrm{Co}/\mathrm{Ho}$ multilayers extending the number of material combinations showing this fascinating property. This ability is studied in wedge-shaped $\mathrm{Co}/\mathrm{Ho}$ multilayers by varying thicknesses and repetition numbers. Surprisingly, even though the spin-orbit coupling is larger than in $\mathrm{Tb}$ and $\mathrm{Dy}$, which should increase the dissipation of angular momentum to the lattice, the pulse duration versus fluence state diagram is close to the one of the $\mathrm{Gd}$-based system.