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We studied (Ba1-xKx)Fe2As2 using high resolution laser ARPES. For BaFe2As2, we found a drastic transformation in Fermi surface (FS) topology with the rearrangement of its orbital component across the transition at TN = 140 K[1]. Polarization-dependent ARPES enables us to separately observe the electronic structure from single domains in the low-temperature twinned structure. It is suggested that single Fe 3d orbital component dominates the highly 3-dimensional FSs in antiferromagnetic (AF) state. We conclude that BaFe2As2 shows AF state coexisting with orbital-polarized metallic state.
We will also discuss on the superconducting gap and its anisotropy of each Fermi surface on (Ba1-xKx)Fe2As2 [2], and KFe2As2 [3] measured by polarization-dependent laser-ARPES. We found that orbital fluctuation mechanism is also important as well as the spin fluctuation mechanism in the superconductivity. We found nodes in the superconducting gaps of KFe2As2 [3]. We discussed about them by d or s+- mechanism
1. T. Shimojima et al., PRL 104, 57002(2010). 2. T. Shimojima et al., Science 332, 564(2011). 3. K.Okazaki et al., unpublished. |
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