Cu doping effects on the electronic structure of Fe1-xCuxSe

TL;DR

This study uses ARPES to analyze how Cu doping alters the electronic structure of FeSe, revealing changes in carrier concentration, band shifts, and effective mass that explain the suppression of superconductivity and emergence of insulating behavior.

Contribution

It provides detailed experimental insights into the electronic structure evolution of FeSe with Cu doping, linking doping effects to superconductivity suppression and magnetic fluctuations.

Findings

Cu introduces extra electrons and shifts hole bands below EF.

Electron pocket size increases but spectral weight decreases.

Effective mass of electron band near M point increases with doping.

Abstract

Using angle-resolved photoemission spectroscopy (ARPES), we studied the evolution of the electronic structure of Fe1-xCuxSe from x = 0 to 0.10. We found that the Cu dopant introduces extra electron carriers. The hole bands near the gamma point are observed to steadily shift downward with increasing doping and completely sink down below the Fermi level (EF) for x > 0.05. Meanwhile, the electron pocket near the M point becomes larger but loses the spectral weight near EF. We also observed that effective mass of the electron band near the M point increases with doping. Our result explains why superconductivity disappears and metal insulator transition (MIT) like behavior occurs upon Cu doping in terms of electronic structure, and provide insight into emergent magnetic fluctuation in Fe1-xCuxSe.