Chiral tunneling in single-layer graphene with Rashba spin-orbit coupling: Spin currents

We study forward scattering of two-dimensional massless Dirac electrons at Fermi energy epsilon > 0 in single-layer graphene (SLG) through a one-dimensional rectangular barrier of height u(0) in the presence of uniform Rashba spin-orbit coupling (of strength lambda). The role of the Klein paradox in graphene spintronics is thereby exposed. It is shown that (1) for epsilon - 2 lambda < u(0) < epsilon + 2 lambda, there is partial Klein tunneling, the transmission coefficient T (lambda) < 1, and quite remarkably, T (lambda >= 0.1 meV) approximate to 0 when the scattering energy equals the barrier height epsilon = u(0) [whereas T (lambda = 0) = 2]. (2) Spin density and spin-current density are remarkably different than in bulk SLG. They are sensitive to lambda and u(0). (3) Spin current densities are space dependent, implying the occurrence of nonzero spin torque density. Such a system may serve as a graphene-based spintronic device without the use of an external magnetic field or magnetic materials.

Automated summary

This study investigates the forward scattering of Dirac electrons in graphene within a rectangular potential barrier, revealing the role of the Klein paradox in graphene spintronics. The research shows that under certain conditions, the transmission coefficient can approximate to zero, with sensitivity to lambda and u(0), and the spin current density exhibits spatial dependence.