Sunday, May 19, 2013

1305.3875 (T. Shimojima et al.)

Pseudogap formation above the superconducting dome in iron-pnictides    [PDF]

T. Shimojima, T. Sonobe, W. Malaeb, K. Shinada, A. Chainani, S. Shin, T. Yoshida, S. Ideta, A. Fujimori, H. Kumigashira, K Ono, Y. Nakashima, H. Anzai, M. Arita, A. Ino, H. Namatame, M. Taniguchi, M. Nakajima, S. Uchida, Y. Tomioka, T. Ito, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki, K. Ohgushi, S. Kasahara, T. Terashima, H. Ikeda, T. Shibauchi, Y. Matsuda, K. Ishizaka
In the normal state above the superconducting transition temperature (Tc), the momentum-resolved electronic structure of the high-Tc cuprate shows a depletion dubbed the psudogap, which becomes less pronounced with doping. Its relation to the high-Tc superconductivity has been a key issue, and the possible rotational symmetry breaking in this state has been reported suggesting a peculiar electronic ordering preceding the superconducting pairing. Here we provide direct evidence for a systematic evolution of the pseudogap phase via angle-resolved photoemission spectroscopy on another family of high-Tc superconductor, iron-pnictides. We observe the P-substitution evolution of pseudogap in BaFe2(As1-xPx)2, which develops well above the magnetostructural transitions and persists above the nonmagnetic superconducting dome, showing a notable similarity with cuprates. In addition, the pseudogap formation is accompanied by inequivalent energy shifts in zx/yz orbitals of iron atoms, indicative of a peculiar iron orbital ordering which breaks the fourfold rotational symmetry.
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