SCALING BEHAVIOR IN PHOTOELECTRON-SPECTRA OF CE-BASED AND YB-BASED HEAVY FERMIONS

The overall shape of photoelectron spectra of heavy fermion systems ha ve been commonly analysed with the single impurity Anderson model (SIA M). We present here two studies providing direct evidences of the Kond o energy scale in the spectra. In the series CeSi(x) (1.6 less-than-or -equal-to x less-than-or-equal-to 2), the controlled and systematic va riation of the Kondo temperature T(K) is reflected by the intensity ev olution of the Kondo resonance around E(F) observed with photoemission and BIS. The typical transformation of the 4f character from itineran t to localised when temperature increases through T(K) is clearly obse rved for the nearly full 4f shell in YbAbCu4. The spectral intensity c lose to E(F) displays the predicted temperature dependence of the Kond o resonance with its crystal field sidebands. This effect is markedly different from the conventional broadening mechanisms occurring in nor mal metals.