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Monday, 28 September 2015

Prof Branislav K. Nikoliã offers an ICN2 Seminar on topological insulators

“What can topological insulators do for spintronics?”. It is the appealing title of the talk offered today at ICN2 by Prof Branislav K. Nikoliã, and introduced by the ICN2 Group Leaders Prof Stephan Roche and Prof Sergio O. Valenzuela.

Prof Branislav K. Nikoliã, from the Department of Physics & Astronomy of the University of Delaware (Newark, USA) offered today an ICN2 Seminar entitled “What can topological insulators do for spintronics?”. The talk was introduced by Prof Stephan Roche and Prof Sergio O. Valenzuela, Group Leaders at ICN2 who develop their research in this field.

Topological insulators (TIs) are newly discovered materials which possess an energy gap in the bulk, akin to conventional band insulators, while hosting metallic surfaces where electrons behave as massless Dirac fermions analogous to the ones found in graphene. However, unlike graphene where spin-orbit coupling (SOC) is negligible due to the lightness of carbon atoms, in TIs it plays a crucial role by locking the direction of spin and momentum of surface electrons. This feature is considered to be a great resource for spintronic applications where combinations of TIs with ferromagnets (FM) could lead to ultralow-power memory and logic devices.

During his talk, the speaker discussed possible routes of integration of TIs and FMs into heterostructures exhibiting: (i) spin-to-charge conversion after the magnetization of the FM layer is brought into steady precession by the microwave absorption; (ii) current-driven spin-orbit torques by which TI surface induces magnetization dynamics of the FM layer; and (iii) spin-Seebeck effect on the surface of TI where temperature gradients driven pure spin currents that can be converted into voltage via the inverse spin Hall effect.