Measurement of Coherent Polarons in the Strongly Coupled   Antiferromagnetically Ordered Iron-Chalcogenide Fe1.02Te using Angle-Resolved   Photoemission Spectroscopy
  The nature of metallicity and the level of electronic correlations in the antiferromagnetically ordered parent compounds are two important open issues for the iron-based superconductivity. We perform a temperature-dependent angle-resolved photoemission spectroscopy study of Fe1.02Te, the parent compound for iron chalcogenide superconductors. Deep in the antiferromagnetic state, the spectra exhibit a "peak-dip-hump" line shape associated with two clearly separate branches of dispersion, characteristics of polarons seen in manganites and lightly-doped cuprates. As temperature increases towards the Neel temperature (T_N), we observe a decreasing renormalization of the peak dispersion and a counterintuitive sharpening of the hump linewidth, suggestive of an intimate connection between the weakening electron-phonon (e-ph) coupling and antiferromagnetism. Our finding points to the highly-correlated nature of Fe1.02Te ground state featured by strong interactions among the charge, spin and lattice and a good metallicity plausibly contributed by the coherent polaron motion. 
Zhongkai Liu, Ruihua He, Donghui Lu, Ming Yi, Yulin Chen, Makoto   Hashimoto, Robert G. Moore, Sung-Kwan Mo, Elizabeth A. No...
cond-mat.str-el cond-mat.supr-con