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 ${\Delta }_{\mathbf{k}}^{\alpha }$, for all momenta $\mathbf{k}$ on the Fermi surface of every band $\alpha$. While there are a variety of techniques for determining $|{\Delta }_{\mathbf{k}}^{\alpha }|$, no general method existed to measure the signed values of ${\Delta }_{\mathbf{k}}^{\alpha }$. Recently, however, a new 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 ${\Delta }_{\mathbf{k}}^{\alpha }$ 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 ${\Delta }_{\mathbf{k}}^{\alpha }$ it generates to the ${\Delta }_{\mathbf{k}}^{\alpha }$ determined from single-atom scattering in FeSe where $s_{\pm }$ 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 ${\Delta }_{\mathbf{k}}^{\alpha }$ of opposite sign.

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Cited by in corpus (5)

• The Three-Dimensional Electronic Structure of LiFeAs: Strong-coupling Superconductivity and Topology in the Iron Pnictides
• Electronic Stripe Patterns Near the Fermi Level of Tetragonal Fe(Se,S)
• Interplay of Hidden Orbital Order and Superconductivity in CeCoIn5
• Quasiparticle interference as a direct experimental probe of bulk odd-frequency superconducting pairing
• General, Strong Impurity-Strength Dependence of Quasiparticle Interference