Possible unconventional superconductivity in iron-based layered compound LaFePO: Study of heat capacity

TL;DR

This study investigates heat capacity in LaFePO and fluorine-doped LaFePO, revealing signs of unconventional superconductivity possibly mediated by spin fluctuations, with notable differences between the two compounds.

Contribution

First heat capacity measurements on LaFePO and its fluorine-doped variant, suggesting unconventional superconductivity driven by electron correlations and spin fluctuations.

Findings

Large electronic heat capacity coefficient in LaFePO

Small normalized heat capacity jump at Tc in LaFePO

Indicators of strong electron correlation and magnetic spin fluctuation

Abstract

Heat capacity measurements were performed on recently discovered iron based layered superconductors, non doped LaFePO and fluorine doped LaFePO. A relatively large electronic heat capacity coefficient and a small normalized heat capacity jump at Tc = 3.3 K were observed in LaFePO. LaFePO0.94F0.06 had a smaller electronic heat capacity coefficient and a larger normalized heat capacity jump at Tc = 5.8 K. These values indicate that these compounds have strong electron electron correlation and magnetic spin fluctuation, which are the signatures of unconventional superconductivity mediated by spin fluctuation.