J un 2 00 0 Ultrafast optical nonlinearity in quasi-one-dimensional Mott-insulator Sr 2 CuO

We report strong instantaneous photoinduced absorption in the quasi-onedimensional Mott insulator Sr2CuO3 in the IR spectral region. The observed photoinduced absorption is to an even-parity two-photon state that occurs immediately above the absorption edge. Theoretical calculation based on a two-band extended Hubbard model explains the experimental… (More)