Nodes of the superconducting gap probed by electronic Raman scattering in HgBa_{2}CaCu_{2}O_{6+\delta } single crystals

TL;DR

This study uses electronic Raman scattering to investigate the superconducting gap in HgBa_{2}CaCu_{2}O_{6+ ext{δ}} crystals, revealing shifted nodes inconsistent with a pure d_{x^{2}-y^{2}} symmetry.

Contribution

It provides direct Raman spectra of the electronic continuum in HgBa_{2}CaCu_{2}O_{6+ ext{δ}} with no phonon interference, revealing shifted nodes in the superconducting gap.

Findings

Raman spectra show a strong linear term in B_{2g} and B_{1g} symmetries.

Nodes are shifted from the [110] and [1ar{1}0] directions.

Results challenge the pure d_{x^{2}-y^{2}} gap symmetry model.

Abstract

Pure electronic Raman spectra with no phonon structures superimposed to the electronic continuum, are reported, in optimally doped HgBa_{2}CaCu_{2}O_{6+\delta } single crystals (T_{c }=126 K). As a consequence, the spectra in the A_{1g }, B_{1g } and B_{2g } symmetries, including the crucial low energy frequency dependence of the electronic scattering, are directly and reliably measured. The B_{2g } and, most strikingly, the B_{1g } spectra exhibit a strong intrinsic linear term, which suggests that the nodes are shifted from the [110] and [1\bar{1}0] directions, a result inconsistent with a pure d_{x^{2}-y^{2}} model.