Multi-atom quasiparticle scattering interference for superconductor energy-gap symmetry determination
Abstract Complete theoretical understanding of the most complex superconductors requires a detailed knowledge of the symmetry of the superconducting energy-gap $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α , for all momenta k on the Fermi surface of every band α. While there are a variety of tec...
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| Autores principales: | , , , , , , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Nature Portfolio
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/97145cbfdfec440a8f2c15b397204a4b |
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| Sumario: | Abstract Complete theoretical understanding of the most complex superconductors requires a detailed knowledge of the symmetry of the superconducting energy-gap $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α , for all momenta k on the Fermi surface of every band α. While there are a variety of techniques for determining $$|{\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha |$$ ∣ Δ k α ∣ , no general method existed to measure the signed values of $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α . Recently, however, a technique based on phase-resolved visualization of superconducting quasiparticle interference (QPI) patterns, centered on a single non-magnetic impurity atom, was introduced. In principle, energy-resolved and phase-resolved Fourier analysis of these images identifies wavevectors connecting all k-space regions where $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α has the same or opposite sign. But use of a single isolated impurity atom, from whose precise location the spatial phase of the scattering interference pattern must be measured, is technically difficult. Here we introduce a generalization of this approach for use with multiple impurity atoms, and demonstrate its validity by comparing the $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α it generates to the $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α determined from single-atom scattering in FeSe where s± energy-gap symmetry is established. Finally, to exemplify utility, we use the multi-atom technique on LiFeAs and find scattering interference between the hole-like and electron-like pockets as predicted for $${\mathrm{{\Delta}}}_{\mathbf{k}}^\alpha$$ Δ k α of opposite sign. |
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