Detecting charge and lattice dynamics in photoinduced charge-order melting in perovskite-type manganites using a 30-femtosecond time resolution

Abstract

We investigated the ultrafast dynamics of photoinduced melting of charge and orbital order in a perovskitetype manganite, Nd 0.5 Ca 0.5 MnO 3 , by means of pump-probe reflection spectroscopy. By irradiation with a 20-fs laser pulse, only the charge sectors become melted within ϳ30 fs through strong electron correlations. During this process the oxygen displacements associated with the ordered phase persist. These displacements are subsequently released accompanied by several coherent oscillations. The coherent oscillation corresponding to the Jahn-Teller mode has relatively large amplitude demonstrating that the orbital order plays a significant role on the stabilization of the charge order.

Numerical study of photoinduced dynamics in a double-exchange model

“…This ultra-fast CO melting and generation of a metallic state are consistent with the recent pump-probe experiments in manganite; a melting of charge order within about 30fs by irradiation was observed. 19 We note that the weakening of the NN spin correlation within few fs is not contradict to the magneto-optical Kerr spectroscopy measurement. In several charge ordered manganites, it was shown that the photo-induced spin dynamics observed by the Kerr spectroscopy is slower than the photo-induced charge dynamics probed by the optical reflection.…”

“…The positive and negative signs of iγ in the denominators of Eq. (19) are for the cases of τ < τ D and τ > τ D , respectively. We focus on the first term in Eq.…”

“…In the numerical calculation, to reduce the computer resource, E n and E l in the denominator of Eq. (19) are replaced by the expectation value for H 0 with respect to the wave function after the pump irradiation, i.e. E p = φ(τ )| H 0 |φ(τ ) .…”

“…8 Electronic and structural phase controlling is also performed by light. [9][10][11][12][13][14][15][16][17][18][19] By photo-irradiation in CO insulating phase, the optical absorption spectra around the charge-transfer excitation shift to lower energy.…”

Photoinduced coherent oscillations in the one-dimensional two-orbital Hubbard model

“…One typical example is coherent oscillations observed after the rapid photoinduced changes. [10][11][12][13][14][15][16][17] These oscillations involve much information of characteristic collective modes of the systems, phonon, orbiton, and so on. Hence investigating the coherent oscillations provides us insight into roles of these modes in the photoinduced phenomena.…”