Time-resolved nonlinear optical spectroscopy of a strongly correlated insulator

Summary form only given. Recently, we have shown how time-resolved nonlinear optical spectroscopy can be utilized to study the spin wave dynamics in strongly correlated systems. Here, we demonstrate how the same techniques can reveal physical properties of higher-energy features, such as the charge transfer (CT) gap. We have performed both linear and nonlinear, time-resolved optical spectroscopy of the charge-transfer exciton on optically thin Sr/sub 2/CuO/sub 2/Cl/sub 2/ single crystals over a wide range of excitation energies and temperatures. We find an anomalously large temperature dependence of the CT exciton in this material, and excitation dynamics, which indicate a two-component decay process. Under photoexcitation at low temperatures, we observe an increase in spectral weight within the energy range of our probe, a property which we ascribe to the strongly correlated nature of the gap.