Uniaxial "nematic-like" electronic structure and Fermi surface of untwinned CaFe2As2

Wang, Qiang; Sun, Zhe; Rotenberg, Eli; Ronning, F.; Bauer, E. D.; Lin, Hsin; Markiewicz, R. S.; Lindroos, M.; Barbiellini, B.; Bansil, Arun; Dessau, D. S.

doi:10.48550/arxiv.1009.0271

Cited by 16 publications

(31 citation statements)

References 31 publications

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“…The magnetic moment we obtained is quite small compared to the previously used value of 0.5 µ B 9 but is close to a recently considered value in theoretical studies 25,26 . It is also consistent with a recently suggested value of 0.19 µ B from single domain ARPES data from CaFe 2 As 2 27 . This probably means that the correlation between electron and magnetic order in the system is not strong, that is, the band calculation overestimates the electronmagnetic order interaction.…”

Section: Resultssupporting

confidence: 92%

Electronic structure of detwinned BaFe2As2from photoemission and first principles

Kim

et al. 2011

Phys. Rev. B

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We performed angle resolved photoelectron spectroscopy (ARPES) studies on mechanically detwinned BaFe2As2. We observe clear band dispersions and the shapes and characters of the Fermi surfaces are identified. Shapes of the two hole pockets around the Γ-point are found to be consistent with the Fermi surface topology predicted in the orbital ordered states. Dirac-cone like band dispersions near the Γ-point are clearly identified as theoretically predicted. At the X-point, split bands remain intact in spite of detwinning, barring twinning origin of the bands. The observed band dispersions are compared with calculated band structures. With a magnetic moment of 0.2 µB per iron atom, there is a good agreement between the calculation and experiment.

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Section: Resultssupporting

confidence: 92%

Electronic structure of detwinned BaFe2As2from photoemission and first principles

Kim

et al. 2011

Phys. Rev. B

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“…However, this result, as mentioned, has been obtained in a weak coupling limit, corresponding to small magnetization, while in this system the ordered magnetic moments are on the order of 1 µ B , and local moments even larger [13][14][15] . Not surprisingly, their Fermi surface is rather far from that measure recently on untwinned samples by Wang et al 16 , while the LDA Fermi surface reproduces it quite well 17 . Indeed, this is a known problem in the weak coupling approach: while being physically justified for the paramagnetic parts of the phase diagram, the Fe magnetism in the ordered phases is driven by the strong local Hund rule coupling, and not by the Fermi surface nesting, as assumed in the weak copling models.…”

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confidence: 60%

Quasiparticle interference in antiferromagnetic parent compounds of iron-based superconductors

2011

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Recently reported quasiparticle interference imaging in underdoped Ca(Fe1−xCox)2As2 shows pronounced C2 asymmetry that is interpreted as an indication of an electronic nematic phase with a unidirectional electron band, dispersive predominantly along the b-axis of this orthorhombic material. On the other hand, even more recent transport measurements on untwinned samples show near isotropy of the resistivity in the ab plane, with slightly larger conductivity along a (and not b). We show that in fact both sets of data are consistent with the calculated ab initio Fermi surfaces, which has a decisevly broken C4, and yet similar Fermi velocity in both directions. This reconciles completely the apparent contradiction between the conclusions of the STM and the transport experiments.PACS numbers: 74.20. Pq,74.25.Jb,74.70.Xa The Fe-based superconductors present a new paradigm for high-T C superconductivity as here Cooper-pairs appear to emerge upon chemical doping from a metallic ground state as opposed from a Mott insulator as found in the celebrated High-T C cuprates 3 . Despite this difference of parent ground state of the Fe-and Cu-based superconductors, similarities lie in that in both cases superconductivity emerges after the suppression of static ordered magnetism 4 . Although band theory has correctly predicted the unusual antiferromagnetic (AFM) order in the parent compounds of the Fe-based superconductors, it consistently overestimates the tendency to magnetism and underestimates the electronic mass, so there is no doubt that electronic interactions can not be ignored in quantitative descriptions, and that they play a different role compared to cuprates. The exact role of correlations, especially once the parent phase of the Fesuperconductors is doped, has been the focus of much debate and controversy.An almost universal feature of the Fe-superconductors is that in the parent phases, there is a tetragonal to orthorhombic structural phase transition that is closely associated with the onset of antiferromagnetic order 5 . Upon chemical doping x, the onset of the structural and magnetic transitions (T S and T N respectively) decrease with x and superconductivity emerges. The physical nature of the cross over from antiferromagnetic order to superconductivity varies between specific materials. In some cases both T S and T N coincide while in others T S is a few degrees higher than T N 5 . Band structure calculations have suggested that the AFM ordering is accompanied by a strong restructuring of the Fermi surface, with the Fermi surface area being reduced by roughly an order of magnitude. This has been confirmed by optical and Hall measurements that register a drastic reduction of the carrier concentration in the AFM state 6 . The calculated AFM Fermi surface consists of several small pockets, which are arranged in the Brillouin zone in a way that strongly breaks the tetragonal symmetry, but each of them is rather isotropic 2 . This led to a prediction of small transport anisotropy. An alternative point of view, th...

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“…Angle-resolved photoemission spectroscopy (ARPES) also observed a dramatic orbital-dependent Fermi-surface reconstruction upon the magnetostructural phase transition. 2,3 However, due to the fact that the crystals used in such experiments spontaneously form dense domains, the signals from the two diagonal phases were mixed in these early experiments. Hence, it was crucial that scanning tunneling microscopy (STM) detected a quasi-one-dimensional interference pattern, 4 thus confirming that the anisotropy arises entirely from a single domain.…”

Section: Introductionmentioning

confidence: 99%

Orbitally and magnetically induced anisotropy in iron-based superconductors

Phillips

2011

Phys. Rev. B

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Recent experimental developments in the iron pnictides have unambiguously demonstrated the existence of in-plane electronic anisotropy in the absence of the long-range magnetic order. Such anisotropy can arise from orbital ordering, which is described by an energy splitting between the two otherwise degenerate dxz and dyz orbitals. Including this phenomenological orbital order into a fiveorbital Hubbard model, we obtain the mean-field solutions where the magnetic order is determined self-consistently. Despite sensitivity of the resulting states to the input parameters, we find that a weak orbital order that places the dyz orbital slightly higher in energy than the dxz orbital combined with intermediate on-site interactions produces band dispersions that are compatible with the photoemission results. In this regime, the stripe antiferromagnetic order is further stabilized and the resistivity displays the observed anisotropy. We also calculate the optical conductivity and show that it agrees with the temperature evolution of the anisotropy seen experimentally.

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Uniaxial "nematic-like" electronic structure and Fermi surface of untwinned CaFe2As2

Cited by 16 publications

References 31 publications

Electronic structure of detwinned BaFe2As2from photoemission and first principles

Electronic structure of detwinned BaFe2As2from photoemission and first principles

Quasiparticle interference in antiferromagnetic parent compounds of iron-based superconductors

Orbitally and magnetically induced anisotropy in iron-based superconductors

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