Broken symmetries, non-reciprocity, and multiferroicity

Abstract

The interplay of space and time symmetries, ferroic properties, chirality and notions of reciprocity determines many of the technologically important properties of materials such as optical diode effect, e.g., in polar ferromagnet FeZnMo3O8. We illustrate these concepts, including the non-reciprocal directional dichroism, through a number of practical examples. In particular, the conditions for non-reciprocity of ferro-rotational order are discussed and the possible use of linear optical gyration is suggested as a way to detect ferro-rotational domains. In addition, we provide the means to achieve high-temperature optical diode effect and elucidate multiferroic behaviors as a result of helical vs. cycloidal spins. Finally, we identify different entities behaving similarly under all symmetry operations, which are useful to understand non-reciprocity and multiferroicity in various materials intuitively.