Superconducting Gap and Pseudogap in Bi-2212

TL;DR

This study uses Raman scattering to investigate the superconducting gap and pseudogap in Bi-2212 crystals across various doping levels, confirming a d-wave order parameter and observing a doping-independent pseudogap energy scale.

Contribution

It provides experimental evidence of a pseudogap in Bi-2212 and details how it evolves with doping, advancing understanding of high-temperature superconductivity.

Findings

Confirmation of d_{x^2-y^2}-wave order parameter

Detection of pseudogap in the normal state

Pseudogap energy scale remains unchanged with doping

Abstract

We present results of Raman scattering experiments in differently doped Bi-2212 single crystals. Below Tc the spectra show pair-breaking features in the whole doping range. The low frequency power laws confirm the existence of a $d_{x^2-y^2}$-wave order parameter. In the normal state between Tc and T* = 200K we find evidence for a pseudogap in B2g symmetry. Upon doping its effect on the spectra decreases while its energy scale appears to be unchanged.