IR pump-probe study of phase separated hole-doped manganite, La1/4Pr3/8Ca3/8MnO3

Ultrafast IR pump-probe spectroscopy is used to investigate La1/4Pr3/8Ca3/8MnO3 (LPCMO). Two types of coherent phonons strongly coupled with charge-ordering (CO) phase are observed. Temperature dependences of coherent phonons are explained by a hypothesis related with CO gap opening. According to the hypothesis, photo-induced electrons relax to acoustic phonon in the paramagnetic phase, but to optical phonons in the CO phase.