Orbital-order phase transition in Pr1−xCaxMnO3 probed by photovoltaics

The orbital-order phase transition in low-doped Pr${}_{1\ensuremath{-}x}$Ca${}_x$MnO${}₃$ ($x$ \ensuremath{\le} 0.3) is investigated through variation of different physical properties, including photovoltaic response, static and ultrafast transient optical absorption, electric transport, magnetization, and lattice structure. The results suggest that spontaneous orbital order emerges at room temperature and thus at much lower temperatures than previously reported. The requisite modification of the famous phase diagram of the manganite is supported by theoretical calculations, which imply that the observed finite orbital polarization above the orbital-order transition temperature is only induced order caused by octahedral tilting.