Anisotropic intrinsic spin relaxation in graphene due to flexural distortions

TL;DR

This paper introduces an intrinsic, anisotropic spin relaxation mechanism in graphene caused by flexural distortions, which could limit spin lifetimes and is relevant for high-quality samples free of extrinsic relaxation sources.

Contribution

The study derives a non-perturbative effective Hamiltonian showing how flexural distortions induce anisotropic spin relaxation in graphene, providing quantitative estimates of spin lifetimes.

Findings

Spin lifetime in graphene can reach microseconds at room temperature.

Spin relaxation rate varies with spin orientation and crystal momentum angle.

Mechanism sets an upper limit for spin lifetimes in high-quality graphene samples.

Abstract

We propose an intrinsic spin scattering mechanism in graphene originated by the interplay of atomic spin-orbit interaction and the local curvature induced by flexural distortions of the atomic lattice. Starting from a multiorbital tight-binding Hamiltonian with spin-orbit coupling considered non-perturbatively, we derive an effective Hamiltonian for the spin scattering of the Dirac electrons due to flexural distortions. We compute the spin lifetime due to both flexural phonons and ripples and we find values in the microsecond range at room temperature. Interestingly, this mechanism is anisotropic on two counts. First, the relaxation rate is different for off-plane and in-plane spin quantization axis. Second, the spin relaxation rate depends on the angle formed by the crystal momentum with the carbon-carbon bond. In addition, the spin lifetime is also valley dependent. The proposed mechanism sets an upper limit for spin lifetimes in graphene and will be relevant when samples of high quality can be fabricated free of extrinsic sources of spin relaxation.