Nonvolatile tuning of the spin–orbit coupling in graphene by a ferroelectric dipole

Abstract

Spin–orbit coupling (SOC) offers an alternative technique for generating pure spin currents in non-magnetic materials and controlling spin precessions for spin-field effect transistors. In addition, introducing SOC into graphene causes pristine graphene to evolve into a new condensed matter phase, such as the topological insulator state (quantum spin Hall state). Thus, the control of SOC in graphene is essential for its functional spin-orbitronic applications. Here, we report the nonvolatile tuning of SOC in graphene through the proximity effect from a ferroelectric substrate, Pb(Zr52,Ti48)O3 (PZT). Ferroelectric poling by applying a gate voltage induces a change in the SOC strength in addition to shifting the charge neutral point in graphene. The variations in SOC were extracted from weak localization within the quantum interference theory of graphene. Our analyses show that the dipole moments from the PZT polarization significantly enhance the z → −z asymmetric and symmetric SOCs of graphene. Unlike the impurity doping and/or gating, our methodology leads to the nonvolatile electrical control of SOC, thereby paving the way for versatile spin-orbitronic applications of graphene.