  An optimal protocol for the current-induced switching of a perpendicularly
magnetized nanoelement placed on the surface of a topological insulator is
presented. The time dependence of both in-plane components of the surface
current that induces the magnetization reversal via Dirac spin-orbit torque
with minimal Joule heating is derived analytically as a function of the
required switching time and material properties. It is demonstrated that a
particularly energy-efficient switching is realized for vanishing dampinglike
torque. The optimal reversal time providing a tradeoff between the switching
speed and energy efficiency is derived. The obtained switching protocol is
contrasted with the one realized in heavy-metal systems. Topological insulators
provide a highly tunable platform for the realization of energy-efficient
magnetization switching.
