Spin excitations and nonlinear optics of quasi–one-dimensional Mott-Hubbard insulators

Laser Physics Applications Division, Raja Ramanna Centre for Advanced Technology - Indore-452013, India

Received: 26 April 2010
Accepted: 7 August 2010

Abstract

The influence of spin excitations on linear and nonlinear optics of quasi–one-dimensional Mott-Hubbard insulators is presented. We show that for one-dimensional strongly correlated electron systems where spin excitations are gapless, linear and nonlinear excitations from the spin excitations can take place. We argue that the spin-excited states belong to “essential states” for nonlinear optical processes but are not coupled to the ground state. Thus conventional expressions for linear, nonlinear optical susceptibilities generally used in conventional semiconductors need to be modified so that manifestations of spin excitations are effective in optical processes. When optical excitations from such spin-excited states are considered in the nonlinear optical susceptibilities, our results reproduce experimental data. This clarifies the origin of some of the new features in nonlinear optical properties observed experimentally recently.