Tailoring Corner States and Exceptional Points in Altermagnets

TL;DR

This paper investigates non-Hermitian topological phenomena in altermagnets, revealing how symmetry-driven dissipation induces phase transitions, exceptional points, and controllable corner states, offering new avenues for magnetic material design.

Contribution

It introduces a universal framework for controlling topological corner states in altermagnets through boundary termination and symmetry considerations, highlighting novel non-Hermitian effects.

Findings

Symmetry-compliant dissipation induces non-Hermitian topological phase transitions.

Hybrid skin-topological modes emerge due to altermagnetic anisotropy.

Corner states are deterministically controlled by boundary sublattice termination.

Abstract

Altermagnets (AMs) exhibit vanishing net magnetization but strong momentum-dependent spin splitting enforced by crystal symmetry. Here, we explore the non-Hermitian effects in dissipative two-dimensional AMs. We show that symmetry-compliant dissipation naturally induces an imaginary staggered exchange field, driving a NH topological phase transition absent in conventional antiferromagnets. In the topologically nontrivial phase, hybrid skin-topological modes driven by altermagnetic d-wave anisotropy emerge, as captured by the chiral skin effect framework. In the gapless phase, we elucidate the creation and annihilation dynamics of exceptional points. Crucially, we analytically prove via the transfer matrix method that corner states are deterministically controlled by the boundary sublattice termination. Owing to the symmetry constraints and the robustness of chiral states, these findings hold universally across all topological AMs. A general framework is established for controlling topological corner states, offering a new strategy for designing magnetic materials with tailored non-Hermitian properties.