The Strong-Coupling Polaron in Electromagnetic Fields

TL;DR

This paper analyzes the behavior of Fr"ohlich polarons under strong electromagnetic fields at large coupling, showing the ground state energy aligns with a scaled Pekar functional and demonstrating polaron binding in magnetic fields.

Contribution

It establishes the leading-order approximation of polaron ground state energy in electromagnetic fields using the Pekar functional with proper scaling.

Findings

Ground state energy matches the Pekar functional minimization

Polaron binding occurs in strong magnetic fields

Results valid in the large coupling limit

Abstract

This paper is concerned with Fr\"ohlich polarons subject to external electromagnetic fields in the limit of large electron-phonon coupling. To leading order in the coupling constant, $\sqrt\alpha$, the ground state energy is shown to be correctly given by the minimum of the Pekar functional including the electromagnetic fields, provided these fields in the Fr\"ohlich model are scaled properly with $\alpha$. As a corollary, the binding of two polarons in strong magnetic fields is obtained.