Symmetry of bipolaron bound states for small Coulomb repulsion

TL;DR

This paper rigorously proves that the ground state of a bipolaron remains spherically symmetric when the Coulomb repulsion between electrons is small, addressing an open question in the field.

Contribution

The paper provides a rigorous mathematical proof that the bipolaron ground state is spherical for small Coulomb repulsion, complementing previous numerical analyses.

Findings

Ground state remains spherical for small Coulomb repulsion

Rigorous proof fills gap left by numerical studies

Clarifies symmetry properties of bipolaron states

Abstract

We consider the bipolaron in the Pekar--Tomasevich approximation and address the question whether the ground state is spherically symmetric or not. Numerical analysis has, so far, not completely settled the question. Our contribution is to prove rigorously that the ground state remains spherical for small values of the electron-electron Coulomb repulsion.