TEMPERATURE-DEPENDENT CHANGE OF CORRELATED ELECTRONIC STATES IN YB4AS3 AND YB-4(AS1-XSBX)(3) PROBED BY HIGH-RESOLUTION PHOTOEMISSION SPECTROSCOPY

Clear changes of the Yb 4f photoemission spectra with temperature are observed in Yb4As3 by high resolution photoemission spectroscopy. The photoemission intensity is very low at the Fermi level and decreases a s the temperature is lowered in accord with the narrowing of the 4f sp ectra. Bulk and surface contributions are deconvoluted in the 4f(13) f inal state spectra. In comparison with the corresponding results in Yb -4(AS(1-x)Sb(x))(3), the spectral changes of Yb4As3 with temperature a re confirmed to be beyond simple thermal broadening effects and relate d to the charge ordering effects. Although the change from the charge ordering temperature (T-t) down to about T-t/2 is consistent with a th eoretical prediction, the change below it is rather unusual and may he ascribed to the incompleteness of the charge ordering effect, Spectra l changes with Yb4Sb3-substitution are qualitatively discussed.