title: Charge ordering fluctuation and optical pseudogap in La(1-x)Ca(x)MnO(3).
abstract: Optical spectroscopy was used to investigate the optical gap ( 2 Delta) due to charge ordering (CO) and related pseudogap developments with x and temperature ( T) in La(1-x)Ca(x)MnO(3) ( 0.48< or =x< or =0.67). Surprisingly, we found 2 Delta/k(B)T(CO) is as large as 30 for x approximately 0.5, and decreases rapidly with increasing x. Simultaneously, the optical pseudogap, possibly starting from T* far above T(CO) becomes drastically enhanced near x = 0.5, producing non-BCS T-dependence of 2 Delta with the large magnitude far above T(CO), and systematic increase of T* for x approximately 0.5. These results unequivocally indicate systematically enhanced CO correlation when x approaches 0.5 even though T(CO) decreases.
authors.affiliation: School of Physics, Seoul National University, Seoul 151-747, Korea.
authors.forename: K H
authors.initials: KH
authors.lastname: Kim
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: T W
authors.initials: TW
authors.lastname: Noh
authors.forename: S-W
authors.initials: SW
authors.lastname: Cheong