Van Hove singularity as a possible origin of the bandwidth renormalization in layered superconductors

We use angle-resolved photoemission spectroscopy to study bandwidth renormalization in layered superconductor 2H-NbSe2. Renormalization of the conduction band in comparison with the very similar 2H-TaSe2 is of the factor of two. We discuss the possibility that the Van Hove singularity could be responsible for this effect not only in dichalcogenides but also in pnictides. (C) 2010 Elsevier Ltd. All rights reserved.