Superlight small bipolarons in the presence of strong Coulomb repulsion

TL;DR

This paper introduces an efficient quantum Monte Carlo method to study small, light bipolarons on various lattices, revealing their potential role in high-temperature superconductivity.

Contribution

It develops a novel CTQMC algorithm for Coulomb-Fröhlich models, enabling detailed analysis of bipolaron properties relevant to superconductivity.

Findings

Bipolarons exhibit crablike motion on studied lattices.

Bipolarons are small and very light over a wide parameter range.

High Bose-Einstein condensation temperatures are possible with these bipolarons.

Abstract

We study a lattice bipolaron on a staggered triangular ladder and triangular and hexagonal lattices with both long-range electron-phonon interaction and strong Coulomb repulsion using a novel continuous-time quantum Monte-Carlo (CTQMC) algorithm extended to the Coulomb-Frohlich model with two particles. The algorithm is preceded by an exact integration over phonon degrees of freedom, and as such is extremely efficient. The bipolaron effective mass and bipolaron radius are computed. Lattice bipolarons on such lattices have a novel crablike motion, and are small but very light in a wide range of parameters, which leads to a high Bose-Einstein condensation temperature. We discuss the relevance of our results with current experiments on cuprate high-temperature superconductors and propose a route to room temperature superconductivity.