Observation of Momentum-Confined In-Gap Impurity State in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Ba</mml:mi></mml:mrow><mml:mrow><mml:mn>0.6</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="normal">K</mml:mi></mml:mrow><mml:mrow><mml:mn>0.4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>As</mml:mi></mml:m

Zhang, P.; Richard, P.; Qian, Tian; Shi, Xun; Ma, Jun; Zeng, Linghui; Wang, X.-P.; Rienks, E. D. L.; Zhang, C.-L.; Dai, Pengcheng; You, Yi-Zhuang; Weng, Zheng-Yu; Wu, Xianxin; Hu, Jiangping; Ding, Hong

doi:10.1103/physrevx.4.031001

Cited by 22 publications

(33 citation statements)

References 36 publications

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“…Similar in-gap states were observed in Ba 0.6 K 0.4 Fe 2 As 2 iron arsenide high temperature superconductor and their origin was attributed to off-plane, non-magnetic disorder 41 . In summary, the temperature and momentum dependent superconducting gaps, on the two σ bands, were systematically studied.…”

Section: −11supporting

confidence: 70%

Momentum dependence of the superconducting gap and in-gap states inMgB2multiband superconductor

et al. 2015

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We use tunable laser based Angle Resolved Photoemission Spectroscopy to study the electronic structure of the multi-band superconductor, MgB2. These results form the base line for detailed studies of superconductivity in multi-band systems. We find that the magnitude of the superconducting gap on both σ bands follows a BCS-like variation with temperature with ∆0 ∼ 7 meV. The value of the gap is isotropic within experimental uncertainty and in agreement with pure a s-wave pairing symmetry. We also observe in-gap states confined to kF of the σ band that occur at some locations of the sample surface. The energy of this excitation, ∼ 3 meV, is inconsistent with scattering from the π band.

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Section: −11supporting

confidence: 70%

Momentum dependence of the superconducting gap and in-gap states inMgB2multiband superconductor

et al. 2015

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“…This interesting gap structure had been discussed in (Ba,K)Fe 2 As 2 experimentally [44,45]. In Appendix A, we show that the hole-s ± -wave gap structure can be obtained in the 3D model for Ba122 system.…”

Section: Introductionsupporting

confidence: 60%

Revisiting orbital-fluctuation-mediated superconductivity in LiFeAs: Nontrivial spin-orbit interaction effects on the band structure and superconducting gap function

et al. 2015

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Precise gap structure in LiFeAs (Tc = 18K) given by ARPES studies offers us significant information to understand the pairing mechanism in iron-based superconductors. The most remarkable characteristics in LiFeAs gap structure would be that "the largest gap emerges on the tiny holepockets around Z point". This result had been naturally explained in terms of the orbital-fluctuation scenario (T. Saito et al., Phys. Rev. B 90, 035104 (2014)), whereas an opposite result is obtained by the spin-fluctuation scenario. In this paper, we study the gap structure in LiFeAs by taking the spin-orbit interaction (SOI) into account, motivated by the recent ARPES studies that revealed the significant SOI-induced modification of the Fermi surface topology. For this purpose, we construct the two possible tight-binding models with finite SOI by referring the bandstructures given by different ARPES groups. In addition, we extend the gap equation for multiorbital systems with finite SOI, and calculate the gap functions by applying the orbital-spin fluctuation theory. On the basis of both SOI-induced band structures, main characteristics of the gap structure in LiFeAs are naturally reproduced only in the presence of strong inter-orbital interactions between (d xz/yz -dxy) orbitals. Thus, the experimental gap structure in LiFeAs is a strong evidence for the orbital-fluctuation pairing mechanism.

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“…In the latter case, the transition from the pure state A with zero gap in the subset II to the pure state B is discontinuous and occurs at a critical U c , given by Eq. (15). The set of non-linear 3 × 3 equations has been analyzed in Refs.…”

Section: Iviii the Selection Of The S-wave Statethe Comparison Withmentioning

confidence: 99%

“…A competing proposal for the same material is a d x 2 −y 2 state, which, according to theory 12 , is mostly concentrated on the third, largest hole pocket. Which superconducting order develops in KFe 2 As 2 and, more generally, in Ba 1−x K x Fe 2 As 2 , is still a subject of debate [13][14][15] , but, in any case, this example shows that superconductivity in FeSCs is not restricted to only one particular s−wave state, unlike in the cuprates, where the superconductivity is believed to be d x 2 −y 2 -wave in all families and at all hole and electron dopings where it exists.…”

Section: Introductionmentioning

confidence: 99%

Superconductivity from repulsion in LiFeAs: Novels-wave symmetry and potential time-reversal symmetry breaking

et al. 2014

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We analyze the structure of the pairing interaction and superconducting gap in LiFeAs by decomposing the pairing interaction for various kz cuts into s− and d-wave components and by studying the leading superconducting instabilities. We use the ten orbital tight-binding model, derived from ab-initio LDA calculations with hopping parameters extracted from the fit to ARPES experiments. We find that the pairing interaction almost decouples between two subsets, one consists of the outer hole pocket and two electron pockets, which are quasi-2D and are made largely out of dxy orbital, and the other consists of the two inner hole pockets, which are quasi-3D and are made mostly out of dxz and dyz orbitals. Furthermore, the bare inter-pocket and intra-pocket interactions within each subset are nearly equal. In this situation, small changes in the intra-pocket and inter-pocket interactions due to renormalizations by high-energy fermions give rise to a variety of different gap structures. We focus on s−wave pairing which, as experiments show, is the most likely pairing symmetry in LiFeAs. We find four different configurations of the s−wave gap immediately below Tc: the one in which superconducting gap changes sign between two inner hole pockets and between the outer hole pocket and two electron pockets, the one in which the gap changes sign between two electron pockets and three hole pockets, the one in which the gap on the outer hole pocket differs in sign from the gaps on the other four pockets, and the one in which the gaps on two inner hole pockets have one sign, and the gaps on the outer hole pockets and on electron pockets have different sign. Different s-wave gap configurations emerge depending on whether the renormalized interactions increase attraction within each subset or increase the coupling between particular components of the two subsets. We discuss the phase diagram and experimental probes to determine the structure of the superconducting gap in LiFeAs. We argue that the state with opposite sign of the gaps on the two inner hole pockets has the best overlap with ARPES data. We also argue that at low T , the system may enter into a "mixed" s + is state, in which the phases of the gaps on different pockets differ by less than π and time-reversal symmetry is spontaneously broken.

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Observation of Momentum-Confined In-Gap Impurity State inBa0.6K0.4Fe2As

Cited by 22 publications

References 36 publications

Momentum dependence of the superconducting gap and in-gap states inMgB2multiband superconductor

Momentum dependence of the superconducting gap and in-gap states inMgB2multiband superconductor

Revisiting orbital-fluctuation-mediated superconductivity in LiFeAs: Nontrivial spin-orbit interaction effects on the band structure and superconducting gap function

Superconductivity from repulsion in LiFeAs: Novels-wave symmetry and potential time-reversal symmetry breaking

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