Observation of Spin-Valley-Coupling-Induced Large Spin-Lifetime Anisotropy in Bilayer Graphene

Johannes Christian Leutenantsmeyer, Josep Ingla-Aynés, Jaroslav Fabian, Bart J. van Wees
2018 Physical Review Letters  
We report the first observation of a large spin lifetime anisotropy in bilayer graphene (BLG) fully encapsulated between hexagonal boron nitride. We characterize the out-of-plane (τ_) and in-plane (τ_∥) spin lifetimes by oblique Hanle spin precession. At 75 K and the charge neutrality point (CNP) we observe a strong anisotropy of τ_/τ_∥ = 8 ± 2. This value is comparable to graphene/TMD heterostructures, whereas our high quality BLG provides with τ_ up to 9 ns, a more than two orders of
more » ... larger spin lifetime. The anisotropy decreases to 3.5 ± 1 at a carrier density of n = 6× 10^11 cm^-2. Temperature dependent measurements show above 75 K a decrease of τ_/τ_∥ with increasing temperature, reaching the isotropic case close to room temperature. We explain our findings with electric field induced spin-valley coupling arising from the small intrinsic spin orbit fields in BLG of 12 μeV at the CNP.
doi:10.1103/physrevlett.121.127702 fatcat:hkaehm6donauxc4pj6a7je57iq