CPM Seminar

Quasi-2D materials for spintronics - Topological Insulators and Graphene

Ching-Tzu Chen

IBM

Novel two-dimensional electronic systems with Dirac-like dispersion present unique opportunities for spintronic applications. In this seminar I will discuss two specific examples.

First we examine the potential of topological insulators as spin-source materials. Using a new spin-polarized tunneling method, giant charge-spin conversion efficiency in topological insulators is revealed, well exceeding that in conventional magnetic tunnel junctions. Through a comparative study between Bi₂Se₃ and (Bi,Sb)₂Te₃, we verify the topological-surface-state origin of the observed giant spin signals and further extract the energy dependence of the effective spin polarization in Bi₂Se₃.

Next we explore the potential of interfacial exchange interaction in 2D materials for spin control and spin generation. Using graphene as a prototype, we demonstrate that its coupling to a model magnetic insulator (EuS) produces a substantial magnetic exchange field (> 14 T), which yields orders-of-magnitude enhancement in the spin signal originated from the Zeeman spin-Hall effect. Furthermore, the strong exchange field lifts the spin degeneracy of graphene in the quantum Hall regime, which may lead to interesting spin-polarized edge transport and thus open up new application space for classical and quantum information processing.