Superconducting materials for large scale applications

Scanlan, R.M.; Malozemoff, A. P.; Larbalestier, D. C.

doi:10.1109/jproc.2004.833673

Cited by 189 publications

(108 citation statements)

References 98 publications

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“…On a more practical level, TBs play a crucial role in the way superconducting vortices move through a superconductor. The dissipative motion of vortices, quantized whirlpools of charge encircling a core with suppressed superconductivity, is a limiting factor in applications of type-II superconductors [29][30][31] . Thus, understanding how TBs affect vortices is important for developing superconductor technologies.…”

Section: Introductionmentioning

confidence: 99%

Diamagnetic vortex barrier stripes in underdopedBaFe2(As1−xPx)2

et al. 2016

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We report magnetic force microscopy (MFM) measurements on underdoped BaFe2(As1−xPx)2 (x = 0.26) that show enhanced superconductivity along stripes parallel to twin boundaries. These stripes of enhanced diamagnetic response repel superconducting vortices and act as barriers for them to cross. The width of the stripes is hundreds of nanometers, on the scale of the penetration depth, well within the inherent spatial resolution of MFM and implying that the width is set by the interaction of the superconductor with the MFM's magnetic tip. Unlike similar stripes observed previously by scanning SQUID in the electron doped Ba(Fe1−xCox)2As2, the stripes in the isovalently doped BaFe2(As1−xPx)2 disappear gradually when we warm the sample towards the superconducting transition temperature. Moreover, we find that the stripes move well below the reported structural transition temperature in BaFe2(As1−xPx)2 and that they can be much denser than in the Ba(Fe1−xCox)2As2 study. When we cool in finite magnetic field we find that some vortices appear in the middle of stripes, suggesting that the stripes may have an inner structure, which we cannot resolve. Finally, we use both vortex decoration at higher magnetic field and deliberate vortex dragging by the MFM magnetic tip to obtain bounds on the strength of the interaction between the stripes and vortices. We find that this interaction is strong enough to play a significant role in determining the critical current in underdoped BaFe2(As1−xPx)2.

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Section: Introductionmentioning

confidence: 99%

Diamagnetic vortex barrier stripes in underdopedBaFe2(As1−xPx)2

et al. 2016

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“…Bitter decoration imaging of larger arrays of vortices in the same material confirmed the vortex disorder [19][20][21], while magnetic force microscopy (MFM) quantified the scaling of vortex disorder with applied field [29]. In underdoped Ba(Fe 0.95 Co 0.05 ) 2 As 2 (T c = 18.5 K), MFM imaging demonstrated the uniformity of the superfluid density at the length scale of the penetration depth λ ab = 325 ± 134509-4 50 nm, and allowed measurement of a typical single-vortex depinning force F depin = 18 pN at T = 5 K in a twin-free, 10-μm-thick sample, corresponding to 1.8 × 10 −6 N/m [27]. Another Bitter decoration study of under-and optimally doped Ba(Fe 1−x Co x ) 2 As 2 found an even larger typical pinning force of order 10 −5 N/m [23].…”

Section: Appendix A: Previous Vortex Imaging Studiesmentioning

confidence: 85%

“…The strength of the pinning force density F P dictates the maximum supercurrent which can be applied without vortex motion and consequent dissipation. Several decades of engineering effort have been devoted to optimizing vortex pinning in superconductors [1][2][3]. However, vortex pinning in the highest-T c cuprate superconductors remains challenging, due in part to the large electronic anisotropy which allows vortices to bend and depin in pancake fragments rather than as one-dimensional semirigid objects [4].…”

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confidence: 99%

Single-vortex pinning and penetration depth in superconductingNdFeAsO1−xFx

et al. 2015

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We use a magnetic force microscope (MFM) to investigate single-vortex pinning and penetration depth in NdFeAsO 1−x F x , one of the highest-T c iron-based superconductors. In fields up to 20 G, we observe a disordered vortex arrangement, implying that the pinning forces are stronger than the vortex-vortex interactions. We measure the typical force to depin a single vortex, F depin 4.5 pN, corresponding to a critical current up to J c 7 × 10 5 A/cm 2 . Furthermore, our MFM measurements allow the first local and absolute determination of the superconducting in-plane penetration depth in NdFeAsO 1−x F x , λ ab = 320 ± 60 nm, which is larger than previous bulk measurements.

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“…Thus tremendous research effort spanning many decades has been devoted to fine-tuning chemical impurities to strengthen vortex pinning without significantly degrading other superconducting metrics. 37,139 Most of this effort is based on tweaking the chemical structure and measuring the bulk critical current, blind to the individual interactions between vortices and specific pinning sites. Interpretation of these bulk experiments can be challenging, particularly in high-T c materials which may already host several forms of inhomogeneity even before the introduction of potential new pinning sites.…”

Section: Chemical Disorder and Vortex Pinningmentioning

confidence: 99%

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Zeljkovic

Hoffman

2013

Phys. Chem. Chem. Phys.

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Many of today's forefront materials, such as high-T c superconductors, doped semiconductors, and colossal magnetoresistance materials, are structurally, chemically and/or electronically inhomogeneous at the nanoscale. Although inhomogeneity can degrade the utility of some materials, defects can also be advantageous. Quite generally, defects can serve as nanoscale probes and facilitate quasiparticle scattering used to extract otherwise inaccessible electronic properties. In superconductors, nonstoichiometric dopants are typically necessary to achieve a high transition temperature, while both structural and chemical defects are used to pin vortices and increase critical current. Scanning tunneling microscopy (STM) has proven to be an ideal technique for studying these processes at the atomic scale.In this perspective, we present an overview of STM studies on chemical disorder in unconventional superconductors, and discuss how dopants, impurities and adatoms may be used to probe, pin or enhance the intrinsic electronic properties of these materials.

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Superconducting materials for large scale applications

Cited by 189 publications

References 98 publications

Diamagnetic vortex barrier stripes in underdopedBaFe2(As1−xPx)2

Diamagnetic vortex barrier stripes in underdopedBaFe2(As1−xPx)2

Single-vortex pinning and penetration depth in superconductingNdFeAsO1−xFx

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

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