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تسجيل مستخدم جديدEvidence for Dirac Nodes from Quantum Oscillations in SrFe$_2$As$_2$
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We present a detailed study of quantum oscillations in the antiferromagnetically ordered pnictide compound SrFe$_2$As$_2$ as the angle between the applied magnetic field and crystalline axes is varied. Our measurements were performed on high quality single crystals in a superconducting magnet, and in pulsed magnetic fields up to 60 T, allowing us to observe orbits from several small Fermi surface pockets. We extract the cyclotron effective mass $m^{star}$ and frequency $F$ for these orbits and track their values as the field is rotated away from the c-axis. While a constant ratio of $m^{star}/F$ is observed for one orbit as expected for a parabolic band, a clear deviation is observed for another. We conclude that this deviation points to an orbit derived from a band with Dirac dispersion near the Fermi level.
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