Electromagnetic properties and electronic structure of the iron-based layered superconductor LaFePO

Kamihara, Yoichi; Hirano, Masahiro; Yanagi, Hiroshi; Kamiya, Toshio; Saitoh, Y.; Ikenaga, Eiji; Kobayashi, Keisuke; Hosono, Hideo

doi:10.1103/physrevb.77.214515

Cited by 75 publications

(53 citation statements)

References 58 publications

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“…2 (b), which may be attributed to the As 4s-4p resonance enhancement [13]. These results suggests the existence of the As 4p contribution hybridized with the Fe 3d sates in the vicinity of EF.…”

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confidence: 57%

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO_0.85

et al. 2008

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Although angle-integrated photoemission spectroscopy (PES) directly allows us to measure the electronic structure and the energy gap, the electronic contributions from those two types of FS sheets are merged in the final states when we used the conventional photon source like a helium discharge lamp. On the other hand, the low-energy tunable photons are very useful for separating out those contributions. With decreasing the photon energy extremely, the photoelectrons are to be observable only from the limited momentum space centered at the Γ point as shown in Fig. 1. Such low-energy high-resolution photoemission measurements have recently performed using a laser giving the photon energy of about 7 eV [4,5]. These studies found a clear pseudogap but did not obtain any sign for the superconducting gap opening.Considering the probing area provided by 7 eV photons, there is no superconducting gap for the hole-like FS sheets around the Γ point. It is thus essential to elucidate the characteristic electronic structure due to the electron-like FS sheets around the M point, in order to understand the pairing mechanism and origin of the superconductivity.In this letter, we report high-resolution photoemission spectroscopy with low-energy tunable photons (LEPES) on oxygen-deficient iron-based oxypnictide superconductors NdFeAsO0.85. We have found a clear shift of the leading-edge away from EF in the superconducting state using 9.5 eV photons. On the other hand, a clear Fermi cutoff with little leading-edge shift can be observed in the case of 6 eV, which is qualitatively consistent with previous laser based photoemission results [4,5]. Present LEPES results demonstrate that the superconducting gap opens on the electron-like FS sheets around the Μ point, but not on the hole-like ones around the Γ point, suggesting that different type of Fermi surface sheets may have a different role in the superconducting states.Polycrystalline samples of NdFeAsO1− δ were synthesized at high pressure and high temperature using a cubic-anvil high-pressure apparatus. Details of synthesis method are given in [6]. Although the nominal oxygen deficiency in the NdFeAsO1− δ samples is 0.35 estimated from the starting materials, recent powder neutron diffraction revealed that the samples are largely shift towards higher oxidation [7].Judging from the relationship between the lattice parameters and the oxygen deficient content, the actual oxygen content used in this experiment is estimated to be 0.85. The

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confidence: 57%

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO_0.85

et al. 2008

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“…A consequence is that, in contrast to the arsenide, the phosphide does not have a magnetic transition (36). We then propose that a parent iron pnictide series created by P doping of As presents a means to unmask a magnetic quantum critical point.…”

Section: As 1−δ P δ Series Of the Parent Iron Pnictidesmentioning

confidence: 99%

Iron pnictides as a new setting for quantum criticality

Dai

Zhu

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

184

193

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Two major themes in the physics of condensed matter are quantum critical phenomena and unconventional superconductivity. These usually occur in the context of competing interactions in systems of strongly-correlated electrons. All this interesting physics comes together in the behavior of the recently discovered iron pnictide compounds that have generated enormous interest because of their moderately high-temperature superconductivity. The ubiquity of antiferromagnetic ordering in their phase diagrams naturally raises the question of the relevance of magnetic quantum criticality, but the answer remains uncertain both theoretically and experimentally. Here we show that the undoped iron pnictides feature a novel type of magnetic quantum critical point, which results from a competition between electronic localization and itinerancy. Our theory provides a mechanism to understand the experimentally-observed variation of the ordered moment among the undoped iron pnictides. We suggest P substitution for As in the undoped iron pnictides as a means to access this new example of magnetic quantum criticality in an unmasked fashion. Our findings point to the iron pnictides as a much-needed new setting for quantum criticality, one that offers a new set of control parameters.Comment: (v3) New abstract, more explanatory material, accepted for PNA

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“…[20,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51] While these differ in detail a number of common features are present. Fig.…”

Section: Crystal Structure and Chemistrymentioning

confidence: 92%

Electronic structure of Fe-based superconductors

Singh

2009

Physica C: Superconductivity

140

114

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Electromagnetic properties and electronic structure of the iron-based layered superconductor LaFePO

Cited by 75 publications

References 58 publications

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO_0.85

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO_0.85

Iron pnictides as a new setting for quantum criticality

Electronic structure of Fe-based superconductors

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Electromagnetic properties and electronic structure of the iron-based layered superconductor LaFePO

Cited by 75 publications

References 58 publications

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO0.85

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO0.85

Iron pnictides as a new setting for quantum criticality

Electronic structure of Fe-based superconductors

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Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO_0.85

Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-Based Oxypnictide Superconductors NdFeAsO_0.85