Strong and Tunable Spin Lifetime Anisotropy in Dual-Gated Bilayer Graphene

TL;DR

This paper reports a significant, electrically tunable spin lifetime anisotropy in dual-gated bilayer graphene, enabling control over spin states with potential applications in spintronics.

Contribution

It demonstrates the first observation of strong, tunable spin lifetime anisotropy in bilayer graphene via electric fields, exploiting spin-valley coupling.

Findings

Spin lifetime up to 7.8 ns achieved

Anisotropy controlled by perpendicular electric field

Out-of-plane spins stabilized by spin-orbit fields

Abstract

We report the discovery of a strong and tunable spin lifetime anisotropy with excellent spin lifetimes up to 7.8 ns in dual-gated bilayer graphene. Remarkably, this realizes the manipulation of spins in graphene by electrically-controlled spin-orbit fields, which is unexpected due to graphene's weak intrinsic spin-orbit coupling. We utilize both the in-plane magnetic field Hanle precession and oblique Hanle precession measurements to directly compare the lifetimes of out-of-plane vs. in-plane spins. We find that near the charge neutrality point, the application of a perpendicular electric field opens a band gap and generates an out-of-plane spin-orbit field that stabilizes out-of-plane spins against spin relaxation, leading to a large spin lifetime anisotropy. This intriguing behavior occurs because of the unique spin-valley coupled band structure of bilayer graphene. Our results demonstrate the potential for highly tunable spintronic devices based on dual-gated 2D materials.