Proximity-induced spin-orbit coupling in graphene/ Bi1.5 Sb0.5 Te1.7 Se1.3 heterostructures

Abstract

The weak intrinsic spin-orbit coupling in graphene can be greatly enhanced by proximity coupling. Here, we report on the proximity-induced spin-orbit coupling in graphene transferred by hexagonal boron nitride (hBN) onto the topological insulator Bi1.5 Sb0.5 Te1.7 Se1.3 (BSTS) which was grown on a hBN substrate by vapor solid synthesis. Phase coherent transport measurements, revealing weak localization, allow us to extract the carrier density-dependent phase coherence length lϕ. While lϕ increases with increasing carrier density in the hBN/graphene/hBN reference sample, it decreases in graphene/BSTS due to the proximity coupling of BSTS to graphene. The latter behavior results from D'yakonov-Perel'-type spin scattering in graphene with a large proximity-induced spin-orbit coupling strength of at least 2.5 meV.