Temperature-dependent angular resolved UV-photoemission spectroscopy from CeNi2Ge2

Pronounced temperature effects in angular resolved ultraviolet photoelectro n spectroscopy from the (001) surface of the ternary heavy fermion compound CeNi2Ge2 are presented. The measurements were performed on atomically clea n and well-ordered thin films grown on a W(110) substrate. A strongly enhan ced intensity at the Fermi edge (E-F) is observed at low-temperatures if th e spectra are excited by means of HeI light (hv=21.2 eV). In addition, the work function is dramatically increased with temperature, exhibiting an unu sually high positive temperature coefficient of about 0.65 meV/K. The obser ved temperature dependency suggests a strong redistribution of the states n ear the Fermi-energy with increasing temperature. A simple model will be gi ven that correlates the observed intensity changes at E-F with the change o f the work function. (C) 2001 Elsevier Science B.V. All rights reserved.