Magnetic Octupole Hall Effect in d-Wave Altermagnets

Abstract: Order parameters not only characterize symmetry-broken equilibrium phases but also govern transport phenomena in the nonequilibrium regime. Altermagnets, a class of magnetic systems integrating ferromagnetic and antiferromagnetic features, host multipolar orders in addition to dipolar Neel order. In this work, we demonstrate the multipole Hall effect in d-wave altermagnets--a transverse flow of multipole moments induced by an electric field. Using symmetry analysis and linear response theory, we show that the magnetic octupole Hall effect persists even in symmetries where the spin-splitter effect is forbidden and thus provides a robust experimental signature. In addition, we identify a sizable electric quadrupole Hall effect, originating from quadrupole splittings in the band structure. Our results expand the family of Hall effects to include higher-order multipolar responses and establish altermagnets as a versatile platform for exploring multipole transport beyond spin and orbital degrees of freedom.