Anisotropic tunneling anomalous Hall effect in altermagnetic tunnel junctions

Abstract

Altermagnets, a novel class of magnetic materials characterized by momentum-dependent collinear spin-splitting in their electronic bands, have garnered considerable research attention. Here, we propose that an anisotropic tunneling anomalous Hall effect can be induced in altermagnetic tunnel junctions. This effect differs fundamentally from the conventional anomalous Hall effect, as it arises from the momentum-dependent spin splitting, rather than from spin-orbit coupling. The Hall conductance, $G_{yx}$, is highly sensitive to the crystallographic orientation of the altermagnet. Specifically, in normal/altermagnet junctions, a pure spin Hall effect without transverse charge current is observed when the altermagnet exhibits $d_{xy}$-wave altermagnetism. In ferromagnet/altermagnet junctions, $G_{yx}$ is highly sensitive to the ferromagnet's magnetization direction, but it vanishes when the altermagnet exhibits $d_{xy}$-wave altermagnetism. Moreover, the Hall angle $G_{yx}/G_{xx}$ can exceed 1, indicating the potential for a large Hall angle. These findings not only demonstrate the feasibility of generating TAHE in altermagnetic junctions, but also highlight its potential for probing d-wave altermagnetism, thereby opening new possibilities for spintronics applications.