Lifting spin degeneracy in rhombohedral trilayer graphene for high magnetoresistance applications

TL;DR

This paper reveals the mechanism of spin degeneracy lifting in rhombohedral trilayer graphene and proposes a novel all-graphene magnetic tunnel junction design for voltage-controlled spintronics, supported by first-principles calculations.

Contribution

It introduces a new design for graphene-based magnetic tunnel junctions utilizing the distinct electronic phases of trilayer graphene.

Findings

Demonstrates voltage control of electronic phases in trilayer graphene.

Shows potential for low-power, fully graphene-based spintronic devices.

Provides detailed electronic structure and transport property analysis.

Abstract

Many exotic properties in rhombohedral (or ABC-stacked) multilayer graphene have recently been reported experimentally. In this Letter, we first reveal the underlying mechanism of spin degeneracy lifting in rhombohedral trilayer graphene. Then, we propose a design concept for all-rhombohedral graphene-based magnetic tunnel junctions (MTJs) by utilizing pristine, back-gated, and top-gated ABC-stacked trilayer graphene, which exhibit semimetallic (conducting), semiconducting (insulating), and half-metallic (ferromagnetic) behavior, respectively. This enables the realization of an "all-in-one" magnetic tunnel junction based entirely on trilayer graphene. This design enables voltage-controlled spintronics (lower power than conventional MTJs) with perfect interfacial matching and sub-nm thickness uniformity across 4-inch wafers. Using first-principles calculations and the non-equilibrium Greens function, we comprehensively study electronic structures and transport properties of these all-graphene MTJs. Furthermore, we demonstrate that their characteristics can be tuned via a perpendicular electric field and electron doping. Our findings offer a new concept for the development of fully graphene-based spintronic devices utilizing the three distinct electronic phases of rhombohedral trilayer graphene.