Temperature-dependent valence-band photoemission study of UNiSn

Abstract

The electronic structure of UNiSn has been investigated using photoemission spectroscopy (PES). The U $5f$ partial spectral weight (PSW) exhibits a broad peak centered at $\ensuremath{\approx}0.3 \mathrm{eV}$ below ${E}_{F}.$ The Ni $3d$ PSW shows the main peak well below ${E}_{F}$ and a very low density of states (DOS) at ${E}_{F}.$ The $h\ensuremath{\nu}$ dependence of the valence-band spectrum reveals a dominant U $5f$ electron character for the states near the Fermi level ${E}_{F},$ with a small contribution from the U $6d,$ Ni $3d,$ and Sn $\mathrm{sp}$ states. Comparison of the measured PES spectra to the $\mathrm{LSDA}+U$ band structure calculation indicates the importance of the on-site Coulomb interaction between U $5f$ electrons in UNiSn. The high-resolution photoemission spectrum of UNiSn is described well by a V-shaped metallic DOS near ${E}_{F},$ suggesting a finite but reduced DOS at ${E}_{F}.$ A possible origin for the reduced DOS at ${E}_{F}$ might be the hybridization of the U $5f$ states to the Ni $3d$ states that have a very low DOS at ${E}_{F}.$ T-dependent high-resolution PES for UNiSn reveals a finite DOS at ${E}_{F}$ even above ${T}_{N}.$