Polar Magnetic Metals by Design

Polar metal with a combination of conflicting polarization and metallicity attracts great research interests recently with promising functionalities. Numerous searches have been carried out particularly in complex oxides with many exciting discoveries. Inspired by the promising magnetoelectric coupling in multiferroic systems with coupled polarity and magnetism, it is of fundamental interest to introduce magnetism (remove time-reversal symmetry) into polar metals to access exotic phases that might emerge through the coupled magnetic and polar orders. The difficulty in realizing a polar magnetic metal lies in circumventing the mutually exclusive requirements of polarity and metallicity, and at the same time incorporating suitable electron correlation effects to form magnetism. In this talk, I will present our recent effort to design and explore novel complex oxides with the breaking of both spatial-inversion and time-reversal symmetries, while maintaining robust metallicity. We further demonstrate that the strong coupling between the polarity and magnetism of these metallic system produces a collection of exotic properties, including the intrinsic magnetochiral anisotropy with exotic magnetic field-free nonreciprocal electrical resistivity, and an emergent Hall effect. We envision that these materials and their derivatives will serve as a model family to probe the rich spectrum of emergent states in complex oxides.