Spin transport in high-mobility graphene on WS${}_2$ substrate with electric-field tunable proximity spin-orbit interaction

Abstract

Graphene supported on a transition metal dichalcogenide substrate offers a novel platform to study the spin transport in graphene in presence of a substrate induced spin-orbit coupling, while preserving its intrinsic charge transport properties. We report the first non-local spin transport measurements in graphene completely supported on a 3.5 nm thick tungsten disulfide (WS${}_2$) substrate, and encapsulated from the top with a 8 nm thick hexagonal boron nitride layer. For graphene, having mobility up to 16,000 cm${}^2$V${}^{-1}$s${}^{-1}$, we measure almost constant spin-signals both in electron and hole-doped regimes, independent of the conducting state of the underlying WS${}_2$ substrate, which rules out the role of spin-absorption by WS${}_2$. The spin-relaxation time ${\tau }_{\text{s}}$ for the electrons in graphene-on-WS${}_2$ is drastically reduced down to~10 ps than ${\tau }_{\text{s}}$ ~ 800 ps in graphene-on-SiO${}_2$ on the same chip. The strong suppression of ${\tau }_{\text{s}}$ along with a detectable weak anti-localization signature in the quantum magneto-resistance measurements is a clear effect of the WS${}_2$ induced spin-orbit coupling (SOC) in graphene. Via the top-gate voltage application in the encapsulated region, we modulate the electric field by 1 V/nm, changing ${\tau }_{\text{s}}$ almost by a factor of four which suggests the electric-field control of the in-plane Rashba SOC. Further, via carrier-density dependence of ${\tau }_{\text{s}}$ we also identify the fingerprints of the D'yakonov-Perel' type mechanism in the hole-doped regime at the graphene-WS${}_2$ interface.

11 pages, 7 figures

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Cited by in corpus (2)

• Spin-orbit driven band inversion in bilayer graphene by van der Waals proximity effect
• Giant proximity exchange and valley splitting in transition metal dichalcogenide/$h\mathrm{BN}$/(Co, Ni) heterostructures