Reconstructing the bulk Fermi surface and superconducting gap properties from neutron scattering experiments

Abstract

We develop an analytical tool to extract bulk electronic properties of unconventional superconductors from inelastic neutron scattering spectra. We show that the upward and downward branches of the spin excitation spectra have distinct origins, with the upper branch representing a gapped spin-wave dispersion and the lower branch associated with Bogoliubov quasiparticle scattering on the Fermi surface. Combined, they produce an ``hourglass'' dispersion with 45${}^{\ensuremath{\circ}}$ rotation of the spectrum, as found experimentally. The downward dispersion can be inverted to reveal the Fermi momentum dispersion of the single-particle spectrum as well as the corresponding superconducting (SC) gap function, analogously to the quasiparticle interference effect in scanning tunneling microscopy (STM). Whereas angle-resolved photoemission spectroscopy and STM provide surface-sensitive information, this inversion procedure provides bulk electronic properties. The technique is essentially model independent and can be applied to a wide variety of materials.

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• Physical Review B - View - PDF