A de Haas-van Alphen study of the Fermi surfaces of superconducting LiFeP and LiFeAs

TL;DR

This study uses de Haas-van Alphen oscillations to analyze the Fermi surfaces of LiFeAs and LiFeP superconductors, revealing topology consistent with calculations and highlighting differences in effective mass enhancements related to their superconducting gap structures.

Contribution

It provides detailed experimental Fermi surface data for LiFeAs and LiFeP, linking mass enhancements and spin fluctuations to their distinct superconducting properties.

Findings

Fermi surface topology matches band-structure calculations

Effective masses are significantly enhanced, especially in LiFeAs

Differences in mass enhancement suggest k-dependent spin fluctuation coupling

Abstract

We report a de Haas-van Alphen (dHvA) oscillation study of the 111 iron pnictide superconductors LiFeAs with T_c ~18K and LiFeP with T_c~5K. We find that for both compounds the Fermi surface topology is in good agreement with density functional band-structure calculations and shows quasi-nested electron and hole bands. The effective masses generally show significant enhancement, up to ~3 for LiFeP and ~5 for LiFeAs. However, one hole Fermi surface in LiFeP shows a very small enhancement, as compared with its other sheets. This difference probably results from k-dependent coupling to spin fluctuations and may be the origin of the different nodal and nodeless superconducting gap structures in LiFeP and LiFeAs respectively.