Quantum-Geometric Fingerprints of Altermagnetic Order in Planar Magnetotransport

TL;DR

This paper demonstrates that planar magnetotransport can serve as a quantum-geometric fingerprint for identifying altermagnetic order in two-dimensional materials by analyzing symmetry-dependent responses to magnetic fields.

Contribution

It introduces a method to detect altermagnetic order via quantum geometric responses in planar magnetotransport, highlighting symmetry-fixed response patterns.

Findings

Linear and nonlinear Hall responses are induced by in-plane Zeeman fields.

Magnetic field susceptibilities reveal distinct patterns for different altermagnetic wave types.

Responses are fixed by the underlying altermagnetic order and symmetry considerations.

Abstract

Identifying altermagnetic order through transport requires signatures that are sensitive to magnetic symmetry but do not rely on a net magnetization. Here we show that planar magnetotransport provides such quantum-geometric fingerprints. In two-dimensional altermagnets with $C_n\mathcal{T}$ magnetic symmetry, an in-plane Zeeman field explicitly breaks the mirror and emergent $C_{2z}$ symmetries that otherwise suppress intrinsic Hall and second-order transport responses. The resulting magnetic field susceptibilities of the Berry curvature and quantum metric produce linear planar Hall, nonlinear planar Hall, and nonreciprocal longitudinal responses. Crucially, the leading magnetic field powers and angular periodicities of these responses are fixed by the underlying altermagnetic order. For $d$-, $g$-, and $i$-wave altermagnets, we find distinct fingerprint patterns associated with quantum geometric susceptibilities. Our results establish planar magnetotransport as a symmetry selective probe of both band quantum geometry and altermagnetic order.