We report quantum oscillation measurements on CaFe2As2 under strong magnetic fields- recently reported to become superconducting under pressures of as little as a kilobar. The largest observed carrier pocket occupies less than 0.05 % of the paramagnetic Brillouin zone volume- consistent with Fermi surface reconstruction caused by antiferromagnetism. On comparing several alkali earth AFe2As2 antiferromagnets (with A=Ca,Sr and Ba), the dependence of both the Fermi surface cross-sectional area F_alpha and the effective mass m*_alpha of the primary observed pocket on the antiferromagnetic/structural transition temperature T_s is found to be consistent with quasiparticles in a conventional spin-density wave model. These findings suggest that a conventional spin-density wave exists within close proximity to superconductivity in this series of compounds, which may have implications for the microscopic origin of unconventional pair formation.
@article{arxiv.0902.1481,
title = {Quantum oscillations in antiferromagnetic CaFe2As2 on the brink of superconductivity},
author = {N. Harrison and R. D. McDonald and C. H. Mielke and E. D. Bauer and F. Ronning and J. D. Thompson},
journal= {arXiv preprint arXiv:0902.1481},
year = {2009}
}