Antiferromagnetic spin valve from heterostructure of two-dimensional hexagonal crystals

TL;DR

This paper proposes and models heterostructure-based antiferromagnetic spin valves using two-dimensional hexagonal crystals, analyzing their electronic and topological properties to enhance spin transport control.

Contribution

It introduces a theoretical framework for antiferromagnetic spin valves with 2D hexagonal crystals, exploring effects of Hubbard interaction and spin-orbit coupling on topological phases.

Findings

Hubbard interaction enlarges the bulk band gap, increasing sensitivity to exchange fields.

Topological phase diagrams guide spin valve design with varied heterostructures.

Coexistence of interactions enlarges topological gaps and improves chiral edge states.

Abstract

Spin valves consisting of heterostructures of single-layer hexagonal crystal on an antiferromagnetic substrate or of bilayer hexagonal crystal intercalated between two (anti)ferromagnetic insulators, with the current-in-plane geometry, are proposed. The two-dimensional hexagonal crystals such as graphene, silicene, germanene, and stanene are modeled by the tight binding model of honeycomb lattice. The magnetization orientation of the antiferromagnetic substrate(s) controls the band gap and topological properties of bulk, which in turn control the transport of three types of spin valve geometries: (i) the in-plane transport of bulk; (ii) the transport of topological edge states along nanoribbon with bulk gap; (iii) the transport of chiral edge state along domain wall. The heterostructures are investigated by a tight binding model with an (anti)ferromagnetic exchange field, Hubbard interaction and(or) spin-orbital coupling. For the first type of spin valve geometry, the Hubbard interaction could enlarged the effective band gap of bulk, which in turn improve the sensitivity of the spin valves to the antiferromagnetic exchange field. For the second and third types of spin valve geometries, the topological phase diagrams of varying types of heterostructures with spin-orbital coupling serve as guideline for designing the spin valve. The coexistence of the Hubbard interaction and the spin-orbital coupling could enlarge the topological gap in bulk and improve the quality of the chiral edge states at the domain walls between regions with different topological numbers.