Electron correlation in FeSe superconductor studied by bulk-sensitive photoemission spectroscopy

TL;DR

This study uses bulk-sensitive photoemission spectroscopy to analyze the electronic structure of FeSe, revealing significant electron correlation effects and a large mass enhancement, consistent with dynamical mean-field theory predictions.

Contribution

It provides the first detailed bulk-sensitive spectral analysis of FeSe, highlighting electron correlation effects and their impact on the electronic structure.

Findings

Large Fe 3d spectral weight near Fermi level

Evidence of band narrowing and energy shift due to correlations

Mass enhancement factor Z^-1=3.6 indicating strong correlations

Abstract

We have investigated the electronic structures of recently discovered superconductor FeSe by soft-x-ray and hard-x-ray photoemission spectroscopy with high bulk sensitivity. The large Fe 3d spectral weight is located in the vicinity of the Fermi level (EF), which is demonstrated to be a coherent quasi-particle peak. Compared with the results of the band structure calculation with local-density approximation, Fe 3d band narrowing and the energy shift of the band toward EF are found, suggesting an importance of the electron correlation effect in FeSe. The self energy correction provides the larger mass enhancement value (Z^-1=3.6) than in Fe-As superconductors and enables us to separate a incoherent part from the spectrum. These features are quite consistent with the results of recent dynamical mean-field calculations, in which the incoherent part is attributed to the lower Hubbard band.