Temperature-Dependent Change of Correlated Electronic States in Yb₄As₃ and Yb₄(As_1-xSb_x)₃ Probed by High Resolution Photoemission Spectroscopy

Abstract

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 as the temperature is lowered in accord with the narrowing of the 4f spectra. Bulk and surface contributions are deconvoluted in the 4f¹³ final state spectra. In comparison with the corresponding results in Yb₄(As_1-xSb_x)₃, the spectral changes of Yb₄As₃ with temperature are confirmed to be beyond simple thermal broadening effects and related 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 theoretical prediction, the change below it is rather unusual and may be ascribed to the incompleteness of the charge ordering effect. Spectral changes with Yb₄Sb₃-substitution are qualitatively discussed.