paper

Signatures of hidden octupolar order from nonlinear Hall effects

arXiv:2311.03435 · doi:10.1103/PhysRevB.110.125127

Abstract

Detecting symmetry-breaking hidden orders with conventional probes has been a long-standing challenge in the field of magnetism. Higher-rank multipolar ordering anisotropic charge and magnetization distributions arising from a combination of spin-orbit coupling and crystalline environments is a quintessential example of such hidden orders, where new protocols of direct detection remain highly desirable. In this work, we propose non-linear Hall effects as a novel probe for multipolar ordering in metallic systems. Taking inspiration from the family of Pr-based heavy-fermion compounds, Pr(Ti,V)Al, we formulate a minimal cubic-lattice model of conduction electrons coupled to a ferro-octupolar order parameter. The time-reversal-breaking order leads to a band structure that supports strong quadrupolar moments of the Berry curvature (BC). Using a semi-classical Boltzmann formalism in conjunction with a symmetry analysis, we demonstrate that the BC quadrupoles produce a third harmonic generation of the Hall voltage measurable in an AC Hall experiment. Properties of the Hall response such as its anisotropy, its dissipationlessness, and its dependence on the order parameter are also examined. Our work encourages a new realm of investigation of multipolar ordering from non-linear transport experiments.

5+5 pages, 4+5 figures; the two authors contributed equally to this work; v2: published in Phys. Rev. B

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