Determining accurate superconducting tunneling energy gaps: Anisotropy in single-crystal Nb

Bostock, J.; Agyeman, Kofi; Frommer, M. H.; MacVicar, M.L.A.

doi:10.1063/1.1662197

Cited by 43 publications

(8 citation statements)

References 2 publications

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“…This gap is smaller than that measured on high quality Nb samples,   1.55 meV (Ref. [28] and figure 5(c)) and the coherence peaks are smeared, which is not surprising in view of the rather low TC of the pristine film (7.4 K). We note that molecules were not found within a few hundred nm from positions where such BCS-type spectra were measured, thus manifesting the localized nature of the chiral-induced OP modification.…”

Section: Figure 1: Topographic Images Of a Nb Film After Polyalanine ...mentioning

confidence: 55%

Unconventional superconductivity induced in Nb films by adsorbed chiral molecules

et al. 2016

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Motivated by recent observations of chiral-induced magnetization and spin-selective transport we studied the effect of chiral molecules on conventional BCS superconductors. By applying scanning tunneling spectroscopy, we demonstrate that the singlet-pairing s-wave order parameter of Nb is significantly altered upon adsorption of chiral polyalanine alpha-helix molecules on its surface. The tunneling spectra exhibit zero-bias conductance peaks embedded inside gaps or gap-like features, suggesting the emergence of unconventional triplet-pairing components with either d-wave or p-wave symmetry at the Nb organic-molecules interface, as corroborated by simulations. These results may open a way for realizing simple superconducting spintronics devices.

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Section: Figure 1: Topographic Images Of a Nb Film After Polyalanine ...mentioning

confidence: 55%

Unconventional superconductivity induced in Nb films by adsorbed chiral molecules

et al. 2016

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“…Electron tunnelling measurement of gap anisotropy in niobium has a long and unsettled history. In a careful study in 1973 Bostock et al [59] conducted tunnelling experiments on niobium single crystals in 26 directions, with carefully prepared indium and lead-bismuth counter-electrodes, only to detect no anisotropy, see TA-BLE V. This conclusion overrode earlier outcomes such as the 1967 MacVicar and Rose study [60] numerous directions and found gap values grouped nonrandomly in k-space. The final view was that there is no observed anisotropy.…”

Section: Niobiummentioning

confidence: 94%

Visualised predictions of gap anisotropy to test new electron pairing scheme

Zheng

Walmsley

2017

Physica C: Superconductivity and its Applications

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The rich and fertile but not yet adequately exploited ground of superconductor anisotropy is proposed as a test bed for a new empirical scheme of electron pairing. The scheme is directed to resolving a numerical and conceptual difficulty in the BCS theory. The original theoretical formulation of the anisotropy problem by Bennett is adopted and its outcomes extensively explored. Here the Bennett conclusion that in metallic superconductors phonon anisotropy is the principal source of gap anisotropy is accepted. Values of the energy gap are visualised globally in k-space with unprecedented detail and accuracy. Comparison is made between the anisotropy pattern from the new and the usual BCS pairing schemes. Differences are revealed for future experimental resolution.

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“…This is a signature of the small gap anisotropy in Nb which agrees well with the prediction made in earlier calculations 24 as well as with experimental observations. [28][29][30][31] It is worthwhile noting that an increased temperature smearing (shown as the orange dashed line) of 1 K strongly suppresses the signature of the gap anisotropy in the DOS which may explain why no gap anisotropy is visible in the STM experiments of Ref. 33 that were done at 1.3 K.…”

Section: A Bulk Nbmentioning

confidence: 99%

“…It is a type-II s-wave superconductor with a fairly large critical temperature of T c ≈ 9.2 K and a large superconducting gap in the electronic structure of 2∆ ≈ 3 meV. Apart from experimental studies, [28][29][30][31][32][33] several ab initio electronic structure calculations are published that investigate the normal state properties [32][33][34][35] or directly calculate superconducting properties. 24,[36][37][38] This abundance of previously published data allows us to benchmark our implementation.…”

Section: Introductionmentioning

confidence: 99%

Density functional Bogoliubov-de Gennes analysis of superconducting Nb and Nb(110) surfaces

Rüßmann,

Blügel

2021

Preprint

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We report on the implementation of the Bogoliubov-de Gennes method into the JuKKR code [https: //jukkr.fz-juelich.de], an implementation of the relativistic all-electron, full-potential Korringa-Kohn-Rostoker Green function method, which allows a material-specific description of inhomogeneous superconductors and heterostructures on the basis of density functional theory. We describe the formalism and report on calculations for the s-wave superconductor Nb, a potential component of the materials platform enabling the realization of the Majorana zero modes in the field of topological quantum computing. We compare the properties of the superconducting state both in the bulk and for (110) surfaces. We compare slab calculations for different thicknesses and comment on the importance of spin-orbit coupling, the effect of surface relaxations and the influence of a softening of phonon modes on the surface for the resulting superconducting gap.

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Determining accurate superconducting tunneling energy gaps: Anisotropy in single-crystal Nb

Cited by 43 publications

References 2 publications

Unconventional superconductivity induced in Nb films by adsorbed chiral molecules

Unconventional superconductivity induced in Nb films by adsorbed chiral molecules

Visualised predictions of gap anisotropy to test new electron pairing scheme

Density functional Bogoliubov-de Gennes analysis of superconducting Nb and Nb(110) surfaces

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