Normal State Correlates of Plasmon-Polaron Superconductivity in Strontium Titanate

TL;DR

This paper models the normal state of SrTiO3 by considering electron-phonon and electron-electron interactions equally, revealing a density-driven crossover dominated by coupled plasmon-phonon oscillations rather than bare phonon features.

Contribution

It introduces a minimal model that treats interactions on equal footing and highlights the dominance of plasmon-phonon oscillations in spectral features.

Findings

Density-driven crossover influenced by bosonic mode adiabaticity

Spectral features dominated by coupled plasmon-phonon oscillations

Deviation from bare phonon features observed in experiments

Abstract

We analyze a minimal model of SrTiO3, such as has been historically used to analyze the superconducting state. Treating the electron-phonon and electron-electron interactions on an equal footing, we calculate the normal state properties, focusing on the spectral function. We find a density-driven crossover caused mostly by the adiabaticity of the bosonic modes, but the spectral features of our theory are dominated by coupled plasmon-phonon oscillations rather than the bare phonon features seen in experiment.