Angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo1.73Fe0.27B2

TL;DR

This study uses angle-resolved photoemission spectroscopy to analyze the electronic structure of LaCo1.73Fe0.27B2, revealing differences from Fe pnictides that suggest a distinct superconducting mechanism.

Contribution

It provides the first detailed electronic structure analysis of LaCo1.73Fe0.27B2, highlighting its unique Fermi surface topology and reduced electron correlation compared to Fe pnictides.

Findings

Fermi level at a dip in the density of states

Higher three-dimensionality of energy bands

Different Fermi surface topology from Fe pnictides

Abstract

We have performed angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo1.73Fe0.27B2 (Tc = 4.1 K), which is isostructural to the 122-type Fe-pnictide superconductor with the pnictogen atom being replaced with boron. We found that the Fermi level is located at a dip in the density of states (DOS) in contrast to Co-pnictide ferromagnets. This reduction in DOS together with the strong Co 3d-B 2p covalent bonding removes the ferromagnetic order and may cause the superconductivity. The energy bands near the Fermi level show higher three dimensionality and a weaker electron-correlation effect than those of Fe pnictides. The Fermi surface topology is considerably different from that of Fe pnictides, suggesting the difference in the superconducting mechanism between boride and pnictide superconductors.