Unlocking Altermagnetism in Antiferromagnetic 2D Films via Adsorption

TL;DR

This paper introduces a symmetry-engineering approach using surface adsorption to induce altermagnetism in 2D antiferromagnetic materials, enabling spin splitting without net magnetization for potential quantum applications.

Contribution

It systematically classifies symmetry operations in 2D antiferromagnets and demonstrates how surface adsorption can selectively break symmetries to realize altermagnetic states.

Findings

Surface adsorption can induce spin splitting in 2D antiferromagnets.

Identified 15 symmetry groups capable of hosting altermagnetism.

First-principles calculations confirm the effectiveness of adsorption strategies.

Abstract

Altermagnets, characterized by zero net magnetization and momentum-dependent spin splitting, have recently garnered significant attention due to their potential applications in a variety of fields. Here, we propose a symmetry-engineering strategy to unlock altermagnetism in two dimensional (2D) antiferromagnetic systems via surface adsorption of atoms or molecules. By employing spin group theory, we systematically demonstrate that selectively breaking symmetry operations, specifically those protecting spin degeneracy in momentum space, enables the emergence of nonrelativistic spin-split electronic states. Meanwhile, preserving rotation or mirror symmetries connecting opposite sublattices ensures zero net magnetization. Through a comprehensive classification of all symmetry operations across 80 layer groups, we identify 63 antiferromagnetic spin point groups (SPGs) describing 2D materials and further isolate 15 groups that can host altermagnetic characteristics through surface adsorption. Exemplified with monolayer antiferromagnetic VPS_3 and MnPSe_3, we show that oxygen adsorption on VPS_3 and NH_3 adsorption on MnPSe_3 selectively disrupt PT symmetry while retaining the [C2||m] symmetry. This engineered symmetry reduction induces pronounced spin splitting in their band structures without spin-orbit coupling, as confirmed by first-principles calculations. Furthermore, adsorption energy analysis and thermal stability phase diagrams under varying coverage regimes reveal optimal configurations for experimental feasibility. Our work establishes a universal symmetry-engineering framework to expand the family of altermagnetic materials, offering a versatile pathway to tailor spin-split functionalities in two-dimensional antiferromagnets for advanced quantum applications.