Superlight small bipolarons from realistic long-range Coulomb and Fr\"ohlich interactions

TL;DR

This paper investigates the properties of bipolarons in a realistic polaronic model with Coulomb and Frohlich interactions, revealing small bipolarons, a phase transition to high-temperature superconductivity, and distinct charge and spin gaps.

Contribution

It provides analytical and numerical analysis of bipolaron states in a realistic long-range interaction model, highlighting the potential for high-temperature superconductivity.

Findings

Ground state is a bipolaronic singlet composed of two polarons.

Bipolaron size remains small across the studied parameter range.

Model predicts a phase transition to superconductivity above 100K.

Abstract

We report analytical and numerical results on the two-particle states of the polaronic t-Jp model derived recently with realistic Coulomb and electron-phonon (Frohlich) interactions in doped polar insulators. Eigenstates and eigenvalues are calculated for two different geometries. Our results show that the ground state is a bipolaronic singlet, made up of two polarons. The bipolaron size increases with increasing ratio of the polaron hopping integral t to the exchange interaction Jp but remains small compared to the system size in the whole range 0<t/Jp<1. Furthermore, the model exhibits a phase transition to a superconducting state with a critical temperature well in excess of 100K. In the range t/Jp<1, there are distinct charge and spin gaps opening in the density of states, specific heat, and magnetic susceptibility well above Tc.