Photoinduced non-reciprocal magnetism

Out of equilibrium, the action-reaction symmetry of the interactions is often broken, leading to the emergence of various collective phenomena with no equilibrium counterparts. Although ubiquitous in classical active systems, implementing such non-reciprocal interactions in solid-state systems has remained challenging, as the known quantum schemes require precise control over the system on a single-site level. Here, we propose a novel dissipation-engineering protocol to induce non-reciprocal interactions in solid-state platforms with light, which we expect to be achievable with state-of-the-art experimental techniques. Focusing on magnetic metals for concreteness, we show microscopically that a light injection that introduces the decay channel to a virtually excited state gives rise to non-reciprocal interactions between localized spins. One can even realize a situation where spin A tries to align with spin B but the B tries the opposite, resulting in a chase-and-runaway dynamics. Applying our scheme to layered ferromagnets, we show that a non-reciprocal phase transition from a static to a many-body time-dependent chiral phase emerges. Our work paves the way to bring solid-state systems to the realm of non-reciprocal science, providing yet another possibility to control quantum matter with light.