Direct observation of the superconducting gap in phonon spectra

TL;DR

This paper demonstrates that phonon spectra can directly reveal the superconducting energy gap and its anisotropy, providing a new spectroscopic method to study superconductors in detail.

Contribution

It introduces a novel application of phonon spectroscopy to directly observe the superconducting gap and analyze its anisotropy in superconductors.

Findings

Superconducting gap observed in phonon spectra.

Phonon spectra can probe gap anisotropy.

Application demonstrated on YNi₂B₂C superconductor.

Abstract

We show that the superconducting energy gap $\Delta$ can be directly observed in phonon spectra, as predicted by recent theories. In addition, since each phonon probes the gap on only a small part of the Fermi surface, the gap anisotropy can be studied in detail. Our neutron scattering investigation of the anisotropic conventional superconductor YNi$_2$B$_2$C demonstrates this new application of phonon spectroscopy.