Evidence of local structural inhomogeneity in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>FeSe</mml:mtext></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Te</mml:mtext></mml:mrow><mml:mi>x</mml:mi></mml:msub></mml:mrow></mml:math>from extended x-ray absorption fine structure

Joseph, Boby; Iadecola, Antonella; Puri, Alessandro; Simonelli, Laura; Mizuguchi, Yoshikazu; Takano, Yoshihiko; Saini, N. L.

doi:10.1103/physrevb.82.020502

Cited by 95 publications

(126 citation statements)

References 39 publications

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“…The Fe-Se bondlength hardly shows any change with temperature unlike the Fe-Fe distance (describing the in-plane lattice parameter) that varies with temperature showing relative flexibility of the later. Figure 4 shows the correlated Debye Waller factors (σ 2 ), i.e., the MSRDs of the Fe-Se and the Fe-Fe pairs as a function of temperature for the K 0.8 Fe 1.6 Se 2 , compared [8]. The solid lines represent the correlated Einstein model fit to the data.…”

Section: Resultsmentioning

confidence: 99%

“…with the σ 2 of the two bondlengths for the binary FeSe system [8]. The σ 2 measured by EXAFS (represents distance broadening) is sum of temperature independent (σ 2 0 ) and temperature dependent terms, i.e.…”

Section: Resultsmentioning

confidence: 99%

“…The FeSe structure contains simple stacking of tetrahedrally coordinated FeSe 4 layers without spacer layers that are known to have substantial effect on the electronic properties [4,5]. Susbstitution by Te in the FeSe leads to a marginal increase in the T c (∼ 15 K), however, the system gets phase separated and the nanoscale structure is characterized by different iron-chalcogen bondlengths [8]. On the other hand, the superconducting transition temperature of the FeSe shows large enhancement up to ∼37 K under the hydrostatic pressure [6,7].…”

Section: Introductionmentioning

confidence: 99%

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Large local disorder in superconducting K_0.8Fe_1.6Se₂studied by extended x-ray absorption fine structure

Iadecola

Joseph

Simonelli

et al. 2012

J. Phys.: Condens. Matter

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We have measured the local structure of superconducting K 0.8 Fe 1.6 Se 2 chalcogenide (T c = 31.8 K) by temperature dependent polarized extended x-ray absorption fine structure (EXAFS) at the Fe and Se K-edges. We find that the system is characterized by a large local disorder. The Fe-Se and Fe-Fe distances are found to be shorter than the distances measured by diffraction, while the corresponding mean square relative displacements reveal large Fe-site disorder and relatively large c-axis disorder. The local force constant for the Fe-Se bondlength (k ∼ 5.8 eV Å−2 ) is similar to the one found in the binary FeSe superconductor, however, the Fe-Fe bondlength appears to be flexible (k ∼ 2.1 eV Å−2 ) in comparison to the binary FeSe (k ∼ 3.5 eV Å−2 ), an indication of partly relaxed Fe-Fe networks in K 0.8 Fe 1.6 Se 2 . The results suggest a glassy nature for the title system, with the superconductivity being similar to that in the granular materials.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Large local disorder in superconducting K_0.8Fe_1.6Se₂studied by extended x-ray absorption fine structure

Iadecola

Joseph

Simonelli

et al. 2012

J. Phys.: Condens. Matter

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“…Further investigations on high quality Te-doped FeSe systems, possibly combining different experimental techniques, are thus mandatory. In particular, since inhomogeneities have been observed in these systems on a nanometer length scale [48,18,7], it will be important to investigate their possible effect on the optical response of a macroscopic sample portion, like that probed by an infrared beam.…”

Section: Discussionmentioning

confidence: 99%

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Perucchi¹,

Joseph²,

Caramazza³

et al. 2014

Supercond. Sci. Technol.

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Abstract. We report an infrared spectroscopy study of a 200 nm thick FeSe 0.5 Te 0.5 film grown on LaAlO 3 with T c =13.7 K. We analyze the 20 K normal state absolute reflectance R N measured over a broad infrared range and the reflectance ratio R S /R N , R S being the superconducting state reflectance, measured at 6 K in the terahertz range down to 12 cm −1 . We show that the normal state model conductivity is given by two Drude components, one of which much broader and intense than the other. In the superconducting state, we find that a gap ∆=37±3 cm −1 opens up in the narrow Drude band only, while the broad Drude band results to be ungapped, at least in the explored spectral range. Our results show that only a two-band model can coherently describe both normal and superconducting state data. ‡ Present address: Elettra Sincrotrone Trieste,

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“…Although the annealed crystal exhibits perfect shielding below T c = 14 K [28], the unannealed crystal separates into superconducting and non-superconducting phases having different chemical composition [35][36][37]. The origin of the phase separation is considered to be a large difference in the Fe-Se and Fe-Te bonding lengths [38]. Figure 7 shows the surface topography and spatial dependence of Q for Fe(Se,Te), acquired in the constant current mode.…”

Section: Imagingmentioning

confidence: 99%

Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator

Takahashi

Imai

Maeda

2016

Review of Scientific Instruments

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We present a design for a tunneling-current-assisted scanning near-field microwave microscope. For stable operation at cryogenic temperatures, making a small and rigid microwave probe is important. Our coaxial resonator probe has a length of approxomately 30 mm and can fit inside the 2-inch bore of a superconducting magnet. The probe design includes an insulating joint, which separates DC and microwave signals without degrading the quality factor. By applying the SMM to the imaging of an electrically inhomogeneous superconductor, we obtain the spatial distribution of the microwave response with a spatial resolution of approximately 200 nm. Furthermore, we present an analysis of our SMM probe based on a simple lumped-element circuit model along with the near-field microwave measurements of silicon wafers having different conductivities.

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Evidence of local structural inhomogeneity inFeSe1−xTexfrom extended x-ray absorption fine structure

Cited by 95 publications

References 39 publications

Large local disorder in superconducting K_0.8Fe_1.6Se₂studied by extended x-ray absorption fine structure

Large local disorder in superconducting K_0.8Fe_1.6Se₂studied by extended x-ray absorption fine structure

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator

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Evidence of local structural inhomogeneity inFeSe1−xTexfrom extended x-ray absorption fine structure

Cited by 95 publications

References 39 publications

Large local disorder in superconducting K0.8Fe1.6Se2studied by extended x-ray absorption fine structure

Large local disorder in superconducting K0.8Fe1.6Se2studied by extended x-ray absorption fine structure

Two-band conductivity of a FeSe$_{0.5}$Te$_{0.5}$ film by reflectance measurements in the terahertz and infrared range

Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator

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Large local disorder in superconducting K_0.8Fe_1.6Se₂studied by extended x-ray absorption fine structure

Large local disorder in superconducting K_0.8Fe_1.6Se₂studied by extended x-ray absorption fine structure