Vacancy-induced nanoscale phase separation in K<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mi>x</mml:mi></mml:msub></mml:math>Fe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi>y</mml:mi></mml:mrow></mml:msub></mml:math>Se<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:

Lazarević, N.; Abeykoon, Milinda; Stephens, Peter W.; Lei, Hechang; Božin, Emil S.; Petrović, C.; Popović, Zoran S.

doi:10.1103/physrevb.86.054503

Cited by 48 publications

(69 citation statements)

References 18 publications

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“…Here, we refer to the latter as the Fe-vacancy-ordered (I4/m VO) model. In this model, the Fe and K occupancies at the low multiplicity sites, 4d and 2b, respectively, were fixed to zero under the assumption that all Fe and K atoms reside only at the high multiplicity sites, 16i and 8h, consistent with our room temperature Rietveld refinements reported earlier [22]. In addition, we considered a modified version of the I4/m model, in which the occupancy of the Fe-vacancy 4d site was allowed to vary, which we refer to as the vacancy-disordered (I4/m VD) model.…”

Section: Model Dependent Pdf Analysissupporting

confidence: 63%

“…The refinements results revealed that, at the nanoscale, the structures of both K x Fe 2−y Se 2 and K x Fe 2−y S 2 within the sensitivity of our data, were consistent with both a two-phase mixture (metallic I4/mmm and insulating I4/m VO) model and with a single phase disordered I4/m VD model. Previous reports confirmed the coexistence of these two phases in both selenide [22] and sulphide analogue [23]. Notably, the single phase I4/m VD model is effectively equivalent to a phase separated model, albeit disordered.…”

Section: Model Dependent Pdf Analysissupporting

confidence: 63%

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On the Nanoscale Structure of KxFe2−yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View

et al. 2018

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Abstract:Comparative exploration of the nanometer-scale atomic structure of K x Fe 2−y Ch 2 (Ch = S, Se) was performed using neutron total scattering-based atomic pair distribution function (PDF) analysis of 5 K powder diffraction data in relation to physical properties. Whereas K x Fe 2−y Se 2 is a superconductor with a transition temperature of about 32 K, the isostructural sulphide analogue is not, which instead displays a spin glass semiconducting behavior at low temperatures. The PDF analysis explores phase separated and disordered structural models as candidate descriptors of the low temperature data. For both materials, the nanoscale structure is well described by the iron (Fe)-vacancy-disordered K 2 Fe 5−y Ch 5 (I4/m) model containing excess Fe. An equally good description of the data is achieved by using a phase separated model comprised of I4/m vacancy-ordered and I4/mmm components. The I4/mmm component appears as a minority phase in the structure of both K x Fe 2−y Se 2 and K x Fe 2−y S 2 , and with similar contribution, implying that the phase ratio is not a decisive factor influencing the lack of superconductivity in the latter. Comparison of structural parameters of the Fe-vacancy-disordered model indicates that the replacement of selenium (Se) by sulphur (S) results in an appreciable reduction in the Fe-Ch interatomic distances and anion heights, while simultaneously increasing the irregularity of FeCh 4 tetrahedra, suggesting the more significant influence of these factors. Structural features are also compared to the non-intercalated FeSe and FeS parent phases, providing further information for the discussion about the influence of the lattice degrees of freedom on the observed properties in layered iron chalcogenides.

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Section: Model Dependent Pdf Analysissupporting

confidence: 63%

Section: Model Dependent Pdf Analysissupporting

confidence: 63%

On the Nanoscale Structure of KxFe2−yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View

et al. 2018

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“…The A 1g mode can be observed for any orientation of the incident light polarization e i provided that the scattered light polarization e s is parallel to it (e s e i ) and will vanish in any crossed polarization configuration (e s ⊥ e i ). On the other hand, the intensity of the B 1g mode strongly depends on the sample orientation (I B1g (Θ) ∼ |c| 2 cos 2 (Θ + 2β) where Θ = ∠(e i , e s ) and β = ∠(e i , x)) 16 . When the sample is oriented so that e i x, (see Figure 2 (a)) one can expect the appearance of both the A 1g and B 1g modes in the parallel and their absence for a cross polarization.…”

Section: Resultsmentioning

confidence: 99%

“…Symmetry considerations predict four Raman-active phonons: A 1g , B 1g and 2E g (Table I) 16 According to the selection rules, the Raman scattering spectra measured from the ab plane of the sample may contain only A 1g and B 1g modes. The A 1g mode can be observed for any orientation of the incident light polarization e i provided that the scattered light polarization e s is parallel to it (e s e i ) and will vanish in any crossed polarization configuration (e s ⊥ e i ).…”

Section: Resultsmentioning

confidence: 99%

Lattice dynamics of KNi2Se2

et al. 2013

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“…4 It is now well documented that superconductivity phase separates from the BAFM and exists in filamentary regions parallel and perpendicular to the FeSe planes. [5][6][7][8][9][10][11][12][13][14][15] In addition to the presence of phase separation, any theoretical description of the superconducting state is necessarily altered compared to the usual iron pnictides by the absence of Fermi surface hole pockets.Experiments find only electron pockets around the M points of 1 Fe Brillouin zone at k z = 0 and the development of additional electron pockets around the Z point. [16][17][18] The description of a spin-fluctuation based pairing mechanism in iron based pnictide superconductors argues for a leading s± pairing instability based on (π, 0) nesting between the electron and hole Fermi surface sheets.…”

Section: Introductionmentioning

confidence: 99%

Impurity-induced subgap bound states in alkali-doped iron chalcogenide superconductors

2013

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Measurements of the local density of states near impurities can be useful for identifying the superconducting gap structure in alkali doped iron chalcogenide superconductors KxFe2−ySe2. Here, we study the effects of nonmagnetic and magnetic impurities within a nearest neighbor d-wave and next-nearest neighbor s-wave superconducting state. For both repulsive and attractive nonmagnetic impurities, it is shown that sub-gap bound states exist only for d-wave superconductors with the positions of these bound states depending rather sensitively on the electron doping level. Further, for such disorder Coulomb interactions can lead to local impurity-induced magnetism in the case of d-wave superconductivity. For magnetic impurities, both s-wave and d-wave superconducting states support sub-gap bound states. The above results can be explained by a simple analytic model that provides a semi-quantitative understanding of the variation of the impurity bound states energies as a function of impurity potential and chemical doping level.

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Vacancy-induced nanoscale phase separation in KxFe2−ySe2

Cited by 48 publications

References 18 publications

On the Nanoscale Structure of KxFe2−yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View

On the Nanoscale Structure of KxFe2−yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View

Lattice dynamics of KNi2Se2

Impurity-induced subgap bound states in alkali-doped iron chalcogenide superconductors

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