NEW METHOD OF NON-FERMI LIQUID STUDY BY PUMP-SUPERCONTINUUM PROBE FEMTOSECOND SPECTROSCOPY

A new method of investigation for the Fermi surface and Fermi liquid ( FL) versus non-Fermi liquid (NFL) behavior in strongly correlated elec tron systems by femtosecond laser spectroscopy is proposed. The method consists in the study of the spectral dependence of the nonequilibriu m charge carrier relaxation time by the pump-supercontinuum probe tech nique. This method is demonstrated on the high T-c oxide-superconducto r YBa2Cu3O7-delta by studying the temporary changes of the optical den sity of a YBa2Cu3O7-delta thin film in a wide spectral region of probi ng <(h)over bar omega(probe)> = 1.6-3.0 eV. The relaxation time sharpl y grows in the spectral area, related to optical transitions in the vi cinity of the Fermi level (or its shadow). The position of this peak g ives the location of the Fermi surface (FS). The form of the peak give s unique information on the damping rate near the FS and thus on the F L versus NFL behavior.