Unconventional Hall effect and magnetoresistance induced by metallic ferroaxial ordering

TL;DR

This paper theoretically investigates how metallic ferroaxial ordering influences unconventional Hall effect and magnetoresistance, highlighting the role of symmetry reduction and electric field effects in transport phenomena.

Contribution

It reveals the essential role of crystalline electric field in ferroaxial-related magnetotransport without requiring spin-orbit coupling, and compares it with conventional Hall effects.

Findings

Ferroaxial ordering induces unconventional Hall effect and magnetoresistance.

Crystalline electric field from symmetry reduction is crucial for ferroaxial magnetotransport.

The effects are observable in candidate materials like Ca$_5$Ir$_3$O$_{12}$.

Abstract

Transport property under metallic ferroaxial ordering in an external magnetic field is theoretically investigated. After presenting the relation between the magnetoconductivity tensor and ferroaxial moment from the symmetry viewpoint, we analyze the behavior of the unconventional Hall effect and magnetoconductivity for a general five $d$-orbital tight-binding model under the point group $C_{\rm 4h}$, where the ferroaxial moment is activated. We show that the crystalline electric field that arises from the symmetry reduction from $D_{\rm 4h}$ to $C_{\rm 4h}$ is essential for the ferroaxial-related magnetotransport, while the relativistic spin-orbit coupling is not required. We also compare the unconventional Hall effect driven by the ferroaxial moment with the conventional Hall effect, the latter of which does not require the ferroaxial moment. The present results provide characteristic transport properties in the ferroaxial systems, which can be observed in various candidate materials like Ca$_5$Ir$_3$O$_{12}$.