A de Haas-van Alphen study of the Fermi surfaces of superconducting   LiFeP and LiFeAs
  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. 
C. Putzke, A. I. Coldea, I. Guillamon, D. Vignolles, A. McCollam, D.   LeBoeuf, M. D. Watson, I. I. Mazin, S. Kasahara, T. T...
cond-mat.supr-con cond-mat.str-el