Research on nonlinear optical materials: an assessment

The seven papers making up this assessment are based on the Workshop on Nonlinear Optical Materials held in April 1986

Organic Superconductors: when correlations and magnetism walk in

This survey provides a brief account for the start of organic superconductivity motivated by the quest for high Tc superconductors and its development since the eighties'. Besides superconductivity found in 1D organics in 1980, progresses in this field of research have contributed to better understand the physics of low dimensional conductors highlighted by the wealth of new remarkable properties. Correlations conspire to govern the low temperature properties of the metallic phase. The contribution of antiferromagnetic fluctuations to the interchain Cooper pairing proposed by the theory is borne out by experimental investigations and supports supercondutivity emerging from a non Fermi liquid background. Quasi one dimensional organic superconductors can therefore be considered as simple prototype systems for the more complex high Tc materials.Comment: 41 pages, 21 figures to be published in Journal of Superconductivity and Novel Magnetis

Origin Of Negative Chi³ In Squaraines: Experimental Observation Of Two-Photon States

Femtosecond pump-probe experiments performed on squaraines demonstrate strong couplings between the first excited state and high-lying two-photon states. The experimental data agree well with our earlier quantum many-electron calculations based on multiple-excited configuration interactions. We show that high-lying two-photon states in squaraines are critically important to understanding the observed third-order optical properties and that two-level models are inadequate even for molecules with negative third-order optical susceptibilities