Unusual x-ray transport phenomena in ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$

An interesting memory effect occurs when ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ $(x\sim 1/8)$ is repeatedly exposed to x rays. While the “dark” conductivity remains unaffected by the irradiation history, the conductivity is markedly enhanced upon exposure to x rays at low temperatures. Immediately after renewed exposure, it recovers the value attained at the end of the previous exposure. We provide a qualitative explanation of this unusual effect in terms of three distinct states with different orbital correlations.