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Evidence for Dirac-like excitations in SrFe2As2 from Quantum Oscillation Experiments

The antiferromagnetic parent compounds of the high 𝑇𝑐 pnictide superconductors play host to unusual magnetic and electronic properties which may be closely related to the presence of superconductivity in the doped compounds. Recent theoretical1 and experimental, 2 work have suggested the presence of small Fermi-surface pockets in these compounds with regions in k-space characterized by a Dirac-like dispersion. Here we test this scenario by performing quantum oscillation studies on high quality single crystal samples of SrFe2As2 to 60 T in pulsed magnetic elds. By tracking the ratio of the quasiparticle e ective mass m⋆ to the quantum oscillation frequency as a function of magnetic eld angle, we observe a dependence consistent with that expected for the Dirac dispersion scenario. We discuss the implications of this result on understanding the metallic state of the FeAs parent compounds. 1 N. Harrison and SE Sebastian, Phys. Rev. B. 80, 224512 (2009). 2 P. Richard P, K. Nakayama, T. Sato et. al., Phys. Rev. Lett. 104, 137001 (2010).

pnictide superconductors; Fermi-surface; Dirac-like dispersion

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