Self-energy effects in electronic Raman spectra of doped cuprates due to magnetic fluctuations

TL;DR

This paper investigates magnetic excitations in doped cuprates and their impact on electronic Raman spectra, revealing how magnetic fluctuations can explain specific spectral features observed experimentally.

Contribution

It introduces a theoretical framework linking magnetic excitations to self-energy effects in Raman spectra of doped cuprates, explaining experimental observations.

Findings

Dispersive quasi-particle excitations in [1,0] direction consistent with RIXS data.

Broad continua dominate excitations near the antiferromagnetic wave vector.

Magnetic fluctuations can produce the observed peak in B₁g Raman spectra below T_c.

Abstract

We present results for magnetic excitations in doped copper oxides using the random phase approximation and itinerant electrons. In the [1,0] direction the observed excitations resemble dispersive quasi-particles both in the normal and superconducting state similar as in recent resonant inelastic X-ray scattering (RIXS) experiments. In the [1,1] direction the excitations form, except for the critical region near the antiferromagnetic wave vector ${\bf Q}=(\pi,\pi)$, only very broad continua. Using the obtained spin propagators we calculate electron self-energies and their effects on electronic Raman spectra. We show that the recently observed additional peak at about twice the pair breaking in B$_{1g}$ symmetry below T$_c$ in HgBa$_2$CuO$_{4+\delta}$ can be explained as a self-energy effect where a broken Cooper pair and a magnetic excitation appear as final states. The absence of this peak in B$_{2g}$ symmetry, which probes mainly electrons near the nodal direction, is explained by their small self-energies compared to those in the antinodal direction.