Doping-Dependent Raman Resonance in the Model High-Temperature Superconductor HgBa2CuO4+d

TL;DR

This study investigates how doping affects Raman resonance in the high-temperature superconductor HgBa2CuO4+d, revealing a doping-dependent shift in resonance conditions linked to inter-band transitions and magnetic fluctuations.

Contribution

It uncovers the doping-dependent change in Raman resonance conditions and connects it to inter-band optical transitions, resolving discrepancies in magnetic fluctuation detection methods.

Findings

Resonant Raman enhancement varies strongly with doping.

Rearrangement of inter-band optical transitions occurs with doping.

Maximum change coincides with peak antinodal superconducting gap.

Abstract

We study the model high-temperature superconductor HgBa2CuO4+d with electronic Raman scattering and optical ellipsometry over a wide doping range. The resonant Raman condition which enhances the scattering cross section of "two-magnon" excitations is found to change strongly with doping, and it corresponds to a rearrangement of inter-band optical transitions in the 1-3 eV range seen by ellipsometry. This unexpected change of the resonance condition allows us to reconcile the apparent discrepancy between Raman and x-ray detection of magnetic fluctuations in superconducting cuprates. Intriguingly, the strongest variation occurs across the doping level where the antinodal superconducting gap reaches its maximum.