Orbital characters of three-dimensional Fermi surfaces in Eu2-xSrxNiO4 as probed by soft-x-ray angle-resolved photoemission spectroscopy

TL;DR

This study uses soft-x-ray ARPES to reveal the three-dimensional Fermi surface of Eu2-xSrxNiO4, showing a multi-band structure with implications for superconductivity in layered nickelates.

Contribution

It provides the first detailed 3D Fermi surface mapping of Eu2-xSrxNiO4, highlighting the proximity of the 3z2-r2 band to the x2-y2 band and its potential impact on superconductivity.

Findings

Identification of a large cylindrical hole Fermi surface.

Observation of a Gamma-centered 3z2-r2-derived small electron pocket.

Multi-band structure with varying orbital character that may hinder high-temperature superconductivity.

Abstract

The three-dimensional Fermi surface structure of hole-doped metallic layered nickelate Eu2-xSrxNiO4 (x=1.1), an important counterpart to the isostructural superconducting cuprate La2-xSrxCuO4, is investigated by energy-dependent soft-x-ray angle-resolved photoemission spectroscopy. In addition to a large cylindrical hole Fermi surface analogous to the cuprates, we observe a Gamma-centered 3z2-r2-derived small electron pocket. This finding demonstrates that in the layered nickelate the 3z2-r2 band resides close to the x2-y2 one in energy. The resultant multi-band feature with varying orbital character as revealed may strongly work against the emergence of the high-temperature superconductivity.