Photoemission spectroscopy across the semiconductor-to-metal transition in FeSi

High-resolution angle-resolved photoemission spectroscopy (ARPES) was performed on high-purity FeSi single crystals. Since a high quality of the surface is obligatory to obtain reliably the correct band structure, special care was taken for the in situ preparation. Comparison of the experimental data with band structure calculations in the local density approximation shows that the self-energy resulting from electronic correlation effects leads to a strong renormalization of the energy bands in the vicinity of the Fermi energy. Temperature-dependent ARPES investigations reveal that at elevated temperatures the self-energy is strongly k-vector-dependent due to scattering of thermally excited particles and holes near the gap. From the ARPES results, it is obvious that the physical properties of FeSi are due to the high DOS at the edge of the renormalized band gap, but are not determined by a Kondo scenario.