Room temperature hidden state in a manganite observed by time-resolved X-ray diffraction

Realizing active quantum control of materials near room temperature is one of the ultimate aims for their practical applications. Recent technological breakthroughs demonstrated that optical stimulation may lead to thermally inaccessible hidden states with unique properties. However, most of the reported hidden states were induced around or below liquid nitrogen temperature. Here, we optically manipulated a manganite near its Curie temperature of 300 K, where typically complex phase competitions locate as well as opportunities for new functionality. A room temperature hidden state was formed with threshold behavior evidenced by a femtosecond paramagnetic to ferromagnetic order switching and a structural change distinct from thermal induced lattice expansion in tens of picoseconds accompanying with phonon softening. We propose that such a hidden state originates from the charge transfer between antiferromagnetic chains after strongly correlated spin-charge quantum excitation, which subsequently initiates an orbital polarization rearrangement described as Mn3x2-r2∕3y2-r23+Mn4+→Mn4+Mn3z2-r23+ and associated non-thermal lattice change. This study started from room temperature yet near a phase transition point, which suggests a new route to create or manipulate novel phases for practical purpose.