Photoemission study of organic and inorganic CDW-systems

We investigate by means of high resolution angular resolved photoemission s pectroscopy the classical one-dimensional organic conductor TTF-TCNQ and th e inorganic one-dimensional conductor (TaSe4)(2)I. We measure dispersive fe atures (1D bands) in accordance with band structure calculations. We observ e typical bulk specific properties like the band periodicities (i.e. the Fe rmi wavevector) and the CDW-gap, which are in agreement with other experime ntal techniques. Peculiar for one-dimensional systems, we do not observe a real Fermi level crossing of a quasi-particle state. Instead the spectral w eight near the chemical potential is strongly suppressed, and we observe a pseudogap in the normal state in both systems. For the organic system our d ata suggest that electronic correlations are important. Our temperature dep endent data further reveal that the pseudogap persists even above the mean field temperature, indicating that CDW-fluctuations cannot account for the pseudogap. For the inorganic compound CDW-fluctuations cannot be neglected in the measured temperature range. Nevertheless the observed energy scare o f the pseudogap is much larger than expected from these fluctuations.