Induced Spin-texture at 3d Transition Metal/Topological Insulator Interfaces

International audienceWhile some of the most elegant applications of topological insulators, such as quantum anomalousHall effect, require the preservation of Dirac surface states in the presence of time-reversal symmetrybreaking, other phenomena such as spin-charge conversion rather rely on the ability for these surfacestates to imprint their spin texture on adjacent magnetic layers. In this work, we investigate thespin-momentum locking of the surface states of a wide range of monolayer transition metals (3d-TM) deposited on top of Bi2Se3topological insulators using first principles calculations. We findan anticorrelation between the magnetic moment of the 3d-TM and the magnitude of the spin-momentum lockinginducedby the Dirac surface states. While the magnetic moment is large in thefirst half of the 3dseries, following Hund’s rule, the spin-momentum locking is maximum in thesecond half of the series. We explain this trend as arising from a compromise between intra-atomicmagnetic exchange and covalent bonding between the 3d-TM overlayer and the Dirac surface states.As a result, while Cr and Mn overlayers can be used successfully for the observation of quantumanomalous Hall effect or the realization of axion insulators, Co and Ni are substantially more efficientfor spin-charge conversion effects, e.g. spin-orbit torque and charge pumpin