Exploring the Dark Side of Cuprate Superconductors: s-wave Symmetry of the Pseudogap

TL;DR

This study combines theory and experiments to demonstrate that the pseudogap in underdoped cuprate superconductors has an s-wave symmetry, differing from the d-wave superconducting gap, and explains various spectral observations.

Contribution

It provides the first comprehensive analysis showing the pseudogap's s-wave symmetry in cuprates, challenging previous assumptions of d-wave symmetry.

Findings

Pseudogap appears in single-electron spectra above the Fermi level in the nodal direction.

Spectral-weight suppression in Raman response is explained by the s-wave pseudogap.

Recent tunneling and photoemission data support the s-wave pseudogap scenario.

Abstract

We reveal the full energy-momentum structure of the pseudogap of underdoped high-Tc cuprate superconductors. Our combined theoretical and experimental analysis explains the spectral-weight suppression observed in the B2g Raman response at finite energies in terms of a pseudogap appearing in the single-electron excitation spectra above the Fermi level in the nodal direction of momentum space. This result suggests an s-wave pseudogap (which never closes in the energy-momentum space), distinct from the d-wave superconducting gap. Recent tunneling and photoemission experiments on underdoped cuprates also find a natural explanation within the s-wave-pseudogap scenario.