title: Complex spectral evolution in a BCS superconductor, ZrB12.
abstract: We investigate the electronic structure of a complex conventional superconductor, ZrB12 employing high resolution photoemission spectroscopy and ab initio band structure calculations. The experimental valence band spectra could be described reasonably well within the local density approximation. Energy bands close to the Fermi level possess t2g symmetry and the Fermi level is found to be in the proximity of quantum fluctuation regime. The spectral lineshape in the high resolution spectra is complex exhibiting signature of a deviation from Fermi liquid behavior. A dip at the Fermi level emerges above the superconducting transition temperature that gradually grows with the decrease in temperature. The spectral simulation of the dip and spectral lineshape based on a phenomenological self energy suggests finite electron pair lifetime and a pseudogap above the superconducting transition temperature.
authors.affiliation: Department of Condensed Matter Physics and Materials' Science, Tata Institute of Fundamental Research, Colaba, Mumbai - 400 005, India.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Thakur
authors.forename: Deepnarayan
authors.initials: D
authors.lastname: Biswas
authors.forename: Nishaina
authors.initials: N
authors.lastname: Sahadev
authors.forename: P K
authors.initials: PK
authors.lastname: Biswas
authors.forename: G
authors.initials: G
authors.lastname: Balakrishnan
authors.forename: Kalobaran
authors.initials: K
authors.lastname: Maiti