Effects of phonon dispersion on the bond-bipolaron superconductivity

TL;DR

This study investigates how optical phonon dispersion influences bipolaron Bose-Einstein condensation and superconductivity, revealing that phonon dispersion can enhance the critical temperature across various regimes and dimensions.

Contribution

It introduces a diagrammatic Monte Carlo approach to analyze phonon dispersion effects on bipolaron condensation, showing dispersion can increase $T_c$ in the bond model.

Findings

$T_c$ remains high over a broad coupling range with dispersive phonons.

Phonon dispersion enhances $T_c$ even in the deep adiabatic regime.

Dispersion is not a limiting factor for high-temperature superconductivity.

Abstract

We employ the diagrammatic Monte Carlo method based on lattice path-integral representaion of the particle sector and real-space diagrammatics of the phonon sector to study effects of optical phonon dispersion on Bose-Einstein condensation of bipolarons in the bond model. For dispersionless phonons with frequency $\omega$ this model was recently shown to give rise to small-size, light-mass bipolarons that undergo a superfluid transition at high values of the $T_c/\omega$ ratio. We find that for dispersive phonons, $T_c$ remains relatively high over a broader range of the coupling strength and even keeps increasing in the deep adiabatic regime both in two and three dimensions. This result implies that phonon dispersion is not a limiting factor in the search for new materials with high superconducting temperatures.