Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling

TL;DR

This paper investigates how Rashba spin-orbit coupling affects spin-dependent Klein tunneling in graphene, revealing behaviors similar to bilayer graphene and uncovering spin separation effects due to the Rashba interaction.

Contribution

It demonstrates the equivalence of monolayer graphene with Rashba coupling to bilayer graphene in transport properties and analyzes spin separation effects in chiral tunneling.

Findings

Chiral tunneling in monolayer graphene with Rashba coupling mimics bilayer graphene.

Normal transmission is suppressed due to spin conservation.

Spin separation occurs via the intrinsic spin-Hall effect.

Abstract

Within an effective Dirac theory the low-energy dispersions of monolayer graphene in the presence of Rashba spin-orbit coupling and spin-degenerate bilayer graphene are described by formally identical expressions. We explore implications of this correspondence for transport by choosing chiral tunneling through pn and pnp junctions as a concrete example. A real-space Green's function formalism based on a tight-binding model is adopted to perform the ballistic transport calculations, which cover and confirm previous theoretical results based on the Dirac theory. Chiral tunneling in monolayer graphene in the presence of Rashba coupling is shown to indeed behave like in bilayer graphene. Combined effects of a forbidden normal transmission and spin separation are observed within the single-band n to p transmission regime. The former comes from real-spin conservation, in analogy with pseudospin conservation in bilayer graphene, while the latter arises from the intrinsic spin-Hall mechanism of the Rashba coupling.