Large spin-relaxation anisotropy in bilayer-graphene/WS${}_2$ heterostructures

Abstract

We study spin-transport in bilayer-graphene (BLG), spin-orbit coupled to a tungsten di sulfide (WS${}_2$) substrate, and measure a record spin lifetime anisotropy ~40-70, i.e. ratio between the out-of-plane ${\tau }_{\perp }$ and in-plane spin relaxation time ${\tau }_{||}$. We control the injection and detection of in-plane and out-of-plane spins via the shape-anisotropy of the ferromagnetic electrodes. We estimate ${\tau }_{\perp }$ ~ 1-2 ns via Hanle measurements at high perpendicular magnetic fields and via a new tool we develop: Oblique Spin Valve measurements. Using Hanle spin-precession experiments we find a low ${\tau }_{||}$ ~ 30 ps in the electron-doped regime which only weakly depends on the carrier density in the BLG and conductivity of the underlying WS${}_2$, indicating proximity-induced spin-orbit coupling (SOC) in the BLG. Such high ${\tau }_{\perp }$ and spin lifetime anisotropy are clear signatures of strong spin-valley coupling for out-of-plane spins in BLG/WS${}_2$ systems in the presence of SOC, and unlock the potential of BLG/transition metal dichalcogenide heterostructures for developing future spintronic applications.

19 figures, 13 pages

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• Ultralong 100 ns Spin Relaxation Time in Graphite at Room Temperature
• Effect of proximity-induced spin-orbit coupling in graphene mesoscopic billiards
• Stabilizing the inverted phase of a WSe${}_2$/BLG/WSe${}_2$ heterostructure via hydrostatic pressure
• Electronic and Spin-Orbit Properties of hBN Encapsulated Bilayer Graphene
• Room-temperature spin-lifetime anisotropy exceeding 60 in bilayer graphene spin valves proximity coupled to WSe${}_2$
• Unprecedented Spin-Lifetime of Itinerant Electrons in Natural Graphite Crystals