Altermagnetic spin textures: Emergent electrodynamics, quantum geometry, and probes

TL;DR

This paper develops a low-energy theory for altermagnetic spin textures, revealing unique emergent electrodynamics and quantum geometric effects that enable local spin control and filtering, with potential applications in spintronics.

Contribution

It introduces the first effective theory for electron dynamics in altermagnetic textures, uncovering novel emergent fields and quantum effects absent in traditional magnetic systems.

Findings

Altermagnetic textures generate emergent electromagnetic fields and quantum-geometric effects.

These effects enable local spin manipulation and differentiation of altermagnetic orders.

A spin-dependent electron lensing mechanism is demonstrated for spin filtering.

Abstract

Emergent electrodynamics arising from spatially and temporally varying magnetic textures provides a framework for spin control in quantum materials. While this principle is established for ferromagnetic and antiferromagnetic textures, its consequences for altermagnets -- magnetic orders with vanishing net magnetization but finite spin splitting -- remain largely unexplored. In this work, we develop an effective low-energy theory of itinerant electrons coupled to smoothly varying altermagnetic spin textures. In the adiabatic regime, we show that altermagnetic textures generate additional emergent electromagnetic fields and quantum-geometric effects that are absent in conventional magnetic systems. These effects include emergent Zeeman fields that encode the structure of the altermagnetic order parameter, enabling local spin manipulation and a way to distinguish different altermagnetic orders. Moreover, we demonstrate a quantum-metric-induced, spin-dependent electron lensing effect that provides a mechanism for spin filtering, and discuss the local admixture of effective odd-parity magnetic components. Our results suggest that textured altermagnets could serve as a versatile resource for spintronics functionalities and a probe of altermagnetism.