Correlations between electronic order and structural distortions and their ultrafast dynamics in the single-layer manganite Pr_0.5Ca_1.5MnO₄

Time-resolved x-ray diffraction experiments on the half-doped single-layered manganite Pr0.5Ca1.5MnO4 are used to monitor the ultrafast photoinduced dynamics of the structural distortion associated with the charge and orbital ordering (CO/OO). As in the nonlayered three-dimensional counterpart, the ordered phase melts in less than 100 fs after 800-nm photoexcitation and subsequently partially recovers due to thermal equilibration of electronic and vibrational systems. Photoexciting Pr0.5Ca1.5MnO4 below the transition temperature of a second structural phase transition that occurs around 146 K (deep inside the CO/OO phase) releases this structural transition, but progresses on a much slower timescale. This additional reduction of crystal symmetry, which we ascribe to a further tilt of the oxygen octahedra, can thus be considered to be only weakly coupled to CO/OO. Furthermore, static hard-x-ray and resonant soft-x-ray diffraction at the MnL2,3 edges experiments identify correlations between structural distortions and electronic order in thermal equilibrium