The temperature-dependent electronic states of FeSi have been studied by using high-resolution angleresolved photoemission spectroscopy ͑ARPES͒ and using low-energy tunable photons. At low temperatures, a peak indicating the valence-band maximum ͑VBM͒ exists at a binding energy of ϳ20 meV along the ⌫R direction. The observed dispersional width of the energy bands is narrower than that given by the bandstructure calculation, and the width of the ARPES peak near the VBM rapidly broadens as the binding energy increases. Analysis of a model self-energy reveals the importance of electron correlation, especially near the VBM. We observed an unusual temperature dependence of the ARPES spectral features near the Fermi level ͑E F ͒: Below ϳ100 K, the peak at the VBM and the energy gap structures are almost unchanged, while at ϳ100-350 K, the peak gradually moves toward E F and the gap is filled. The present results indicate that FeSi is a strongly correlated semiconductor, with a renormalized band near E F being responsible for the rapid collapse of the peak and the coherent energy gap upon heating.

Valence band changes in Sb2-xInxTe3 and Sb2Te3-ySey by transprot and Shubnikovde Haas effect measurements Kulbachinskii, V.A.; Dashevski, Z.M.; Inoue, M.; Sasaki, M.; Negishi, H.; Gao, W.X.; Lostak, P.; Horak, J.; de Visser, A.

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