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تسجيل مستخدم جديدQuantum oscillations in the parent pnictide BaFe$_2$As$_2$ : itinerant electrons in the reconstructed state
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We report quantum oscillation measurements that enable the direct observation of the Fermi surface of the low temperature ground state of ba122. From these measurements we characterize the low energy excitations, revealing that the Fermi surface is reconstructed in the antiferromagnetic state, but leaving itinerant electrons in its wake. The present measurements are consistent with a conventional band folding picture of the antiferromagnetic ground state, placing important limits on the topology and size of the Fermi surface.
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We revisit the electronic structure of BaFe$_2$As$_2$, the archetypal parent compound of the Fe-based superconductors, using angle-resolved photoemission spectroscopy (ARPES). Our high-resolution measurements of samples detwinned by the application o
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et al.}, Nat. Mater. 14, 1008-1012 (2015); T. Yamauchi {it et al.}, Phys. Rev. Lett. 115, 246402 (2015)]. By fitting the spherically averaged experimental data collected on a powder sample to a Heisenberg Hamiltonian, we find that the one-dimensional antiferromagnetic ladder exhibits a strong nearest neighbor ferromagnetic exchange interaction ($SJ_R=-71pm4$ meV) along the rung direction, an antiferromagnetic $SJ_L=49pm3$ meV along the leg direction and a ferromagnetic $SJ_2=-15pm2$ meV along the diagonal direction. Our data demonstrate that the antiferromagnetic spin excitations are a common characteristic for the iron-based superconductors, while specific relative values for the exchange interactions do not appear to be unique for the parent states of the superconducting materials.
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