Evolution of Magnetic and Superconducting Fluctuations with Doping of High-Tc Superconductors (An electronic Raman scattering study)

TL;DR

This study uses electronic Raman scattering to investigate how magnetic and superconducting fluctuations evolve with doping in high-Tc cuprate superconductors, revealing persistent antiferromagnetic correlations and the development of coherence leading to superconductivity.

Contribution

It provides new insights into the doping-dependent evolution of magnetic and superconducting fluctuations using Raman spectroscopy in cuprates.

Findings

Persistent short-range AF correlations with doping

Observation of a sharp B1g Raman resonance above T_c

Detection of a pseudogap below 75 meV in the normal state

Abstract

For YBa_2Cu_3O_{6+\delta} and Bi_2Sr_2CaCu_2O_8 superconductors, electronic Raman scattering from high- and low-energy excitations has been studied in relation to the hole doping level, temperature, and energy of the incident photons. For underdoped superconductors, it is concluded that short range antiferromagnetic (AF) correlations persist with hole doping and doped single holes are incoherent in the AF environment. Above the superconducting (SC) transition temperature T_c the system exhibits a sharp Raman resonance of B_1g symmetry and about 75 meV energy and a pseudogap for electron-hole excitations below 75 meV, a manifestation of a partially coherent state forming from doped incoherent quasi-particles. The occupancy of the coherent state increases with cooling until phase ordering at T_c produces a global SC state.