Nature Commun. 6, 6179 (2015)

As the nature of charge carriers is intimately linked to a material's symmetry, the inherent symmetry breaking that occurs at edges can give rise to states with markedly different characteristics than those in the bulk. Symmetry-induced edge states have been observed in several systems, such as graphene and topological insulators, but Kai Du and co-workers have now revealed that intrinsic edge states can also exist in strongly correlated oxides.

The correlation between lattice, spin, charge and orbital degrees of freedom in perovskite manganites leads to a rich phase diagram that includes ferromagnetic and antiferromagnetic states, so several electronic phases often coexist. Du et al. provided evidence that symmetry breaking of the antiferromagnetic charge-ordered state actually induces ferromagnetic metallic edge states in manganite strips, which could even survive at room temperature — well above temperatures at which the ferromagnetic phases away from the edge can exist. As these symmetry-induced states have much higher metal–insulator transition temperatures, they provide a means for tuning the electron phase separation by simply changing the sample size and geometry.