Nanoscale superconducting-gap variations and lack of phase separation in optimally doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>BaFe</mml:mtext></mml:mrow><mml:mrow><mml:mn>1.86</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Co</mml:mtext></mml:mrow><mml:mrow><mml:mn>0.14</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>As</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Massee, F.; Huang, Yingkai; Huisman, R.; Jong, S. de; Goedkoop, J. B.; Golden, M. S.

doi:10.1103/physrevb.79.220517

Cited by 90 publications

(116 citation statements)

References 30 publications

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“…The gap size 2∆ is similar for all the samples, ranging from 24 to 40 meV. This gap size is much larger than those previously ob- served by STM (∼12 meV) [10,11] and ARPES (13 and 10 meV for different Fermi surfaces) [22] on the striped surface, which were attributed to the isotropic s-wave superconducting gap. The universality of the observed gap feature on the √ 2 × √ 2 surfaces strongly indicates that they share the same origin.…”

mentioning

confidence: 68%

“…The first is the widely observed stripe structure (not shown) [9,10,11]. The other type of surface is atomically flat, as shown in Fig.…”

mentioning

confidence: 95%

“…Stripe [9,10,11] or square-lattice [12,13,14] structures were observed at the surfaces of some certain compounds. However, the surface termination of the 122-type pnictides is still in debate, and the evolution of the geometric and electronic structures as a function of doping level has never been explored at atomic scale.…”

mentioning

confidence: 99%

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2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−x
Zhang
¹
,
Dai²,
Zhang³
et al. 2010
Phys. Rev. B
37
4
32
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mentioning

confidence: 68%

“…The first is the widely observed stripe structure (not shown) [9,10,11]. The other type of surface is atomically flat, as shown in Fig.…”

mentioning

confidence: 95%

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2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−x
Zhang
¹
,
Dai²,
Zhang³
et al. 2010
Phys. Rev. B
37
4
32
0
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“…Recent STS studies have reported substantial variations of the value of the superconducting gap on a scale of 10 to 20 nm. 7,11 These local variations of the gap magnitude should correspond to the variations of the critical temperature and therefore lead to vortex pinning. Although it is tempting to relate our results to the nanoscale disorder observed in the STS gap-maps, it should be remarked that the spatial scale of the variations in the gap maps is a factor of 3-6 smaller than that found from the analysis of the data presented here.…”

Section: Discussionmentioning

confidence: 99%

Strong pinning and vortex energy distributions in single-crystalline Ba(Fe1−xCox)2

et al. 2011

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The interrelation between heterogeneity and flux pinning is studied in Ba(Fe1−xCox)2As2 single crystals with widely varying Co-content x. Magnetic Bitter decoration of the superconducting vortex ensemble in crystals with x = 0.075 and x = 0.1 reveal highly disordered vortex structures. The width of the Meissner belt observed at the edges of the crystals, and above the surface steps formed by cleaving, as well as the width of the intervortex distance distribution, indicate that the observed vortex ensemble is established at a temperature just below the critical temperature Tc. The vortex interaction energy and pinning force distributions extracted from the images strongly suggest that the vortex lattice disorder is attributable to strong pinning due to spatial fluctuations of Tc and of the superfluid density. Correlating the results with the critical current density yields a typical length scale of the relevant disorder of 40 -60 nm.

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“…On the contrary, the STM/STS studies on the '122' family are still controversial although great efforts have been put in the studies [5][6][7][8][9][10][11][12] , with main debate focused on where and how the crystal cleaves. For example, within the BaFe 2 As 2 (Ba122) unit cell, the Fe-As layers have a mirror symmetry around the Ba layer as shown in Fig.…”

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confidence: 99%

Effect of Surface Morphology and Magnetic Impurities on the Electronic Structure in Cobalt-Doped BaFe₂As₂ Superconductors

Zou

et al. 2017

Nano Lett.

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Combined scanning tunneling microscopy, spectroscopy and local barrier height (LBH) studies show that low-temperature-cleaved optimally-doped Ba(Fe 1-x Co x ) 2 As 2 crystals with x=0.06, with T c = 22 K, have complicated morphologies. Although the cleavage surface and hence the morphologies are variable, the superconducting gap maps show the same gap widths and nanometer size inhomogeneities irrelevant to the morphology. Based on the spectroscopy and LBH maps, the bright patches and dark stripes in the morphologies are identified as Ba and As dominated surface terminations, respectively. Magnetic impurities, possibly due to cobalt or Fe atoms, are believed to create local in-gap state and in addition suppress the superconducting coherence peaks. This study will clarify the confusion on the cleavage surface terminations of the Fe-based superconductors, and its relation with the electronic structures.One major difference between the iron-based superconductors (FeSC) and conventional superconductors is the necessary involvement of magnetic elements. For a long time magnetic elements had been thought to suppress the superconductivity because of the competitive nature of superconductivity and magnetism, but with the cuprates and now FeSC, there are two cases of high-temperature superconductivity that apparently are magnetic in origin [1][2][3][4] .FeSC share a common Fe 2 X 2 layer structure where X is a pnictogen (P, As) or a chalcogen (S, Se, Te). With the incorporation of intercalation layers between the Fe 2 X 2 layers, FeSC are classified into five families: '11', '111', '122', '1111' and complex structure materials 3-4 . To understand the causes of this superconductivity, the relationship between the global properties and local behavior must be understood. These local signatures include chemical defects, electronic variations, dopant distributions, and strain. The '11' and '111' families have been studied extensively using scanning tunneling microscopy and spectroscopy (STM/STS) and the results are clear due to the cleanness of the cleavage as there is unique and symmetric cleavage plane, 1 and a non-polar surface with minimal surface effect [5][6] . On the contrary, the STM/STS studies on the '122' family are still controversial although great efforts have been put in the studies [5][6][7][8][9][10][11][12] , with main debate focused on where and how the crystal cleaves. For example, within the BaFe 2 As 2 (Ba122) unit cell, the Fe-As layers have a mirror symmetry around the Ba layer as shown in Fig. 1 (a). As FeAs layer is a highly polar plane, the physical cleavage through this plane might force Ba ions to be divided to both sides of the cleavage surface to alleviate the polar nature, associated with surface reconstructing. As a result, rich morphologies or "terminations" exist on the Ba122 cleavage surface. Some groups report that the crystal cleaves at Ba plane with ½ monolayer of Ba atoms to achieve the charge neutral surface 7-10 , while others suggest As atoms terminate the surface by breaking the we...

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Nanoscale superconducting-gap variations and lack of phase separation in optimally dopedBaFe1.86Co0.14As2

Cited by 90 publications

References 30 publications

2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−x
Zhang
¹
,
Dai²,
Zhang³
et al. 2010
Phys. Rev. B
37
4
32
0
View full text Add to dashboard Cite

2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−x
Zhang
¹
,
Dai²,
Zhang³
et al. 2010
Phys. Rev. B
37
4
32
0
View full text Add to dashboard Cite

Strong pinning and vortex energy distributions in single-crystalline Ba(Fe1−xCox)2

Effect of Surface Morphology and Magnetic Impurities on the Electronic Structure in Cobalt-Doped BaFe₂As₂ Superconductors

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Nanoscale superconducting-gap variations and lack of phase separation in optimally dopedBaFe1.86Co0.14As2

Cited by 90 publications

References 30 publications

2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−xZhang1, Dai2, Zhang3 et al. 2010Phys. Rev. B374320View full textAdd to dashboardCite

2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−xZhang1, Dai2, Zhang3 et al. 2010Phys. Rev. B374320View full textAdd to dashboardCite

Strong pinning and vortex energy distributions in single-crystalline Ba(Fe1−xCox)2

Effect of Surface Morphology and Magnetic Impurities on the Electronic Structure in Cobalt-Doped BaFe2As2 Superconductors

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Product

Resources

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2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−x
Zhang
¹
,
Dai²,
Zhang³
et al. 2010
Phys. Rev. B
37
4
32
0
View full text Add to dashboard Cite

2×2structure and charge inhomogeneity at the surface of superconductingBaFe2−x
Zhang
¹
,
Dai²,
Zhang³
et al. 2010
Phys. Rev. B
37
4
32
0
View full text Add to dashboard Cite

Effect of Surface Morphology and Magnetic Impurities on the Electronic Structure in Cobalt-Doped BaFe₂As₂ Superconductors