Radiative spin polarization in an ultrastrong magnetic field

TL;DR

This paper calculates electron spin flip rates in strong magnetic fields for low energy states, revealing that existing models overestimate polarization in this regime, which is relevant for understanding quantum electrodynamics under extreme conditions.

Contribution

It provides new calculations of spin flip rates for low excitations in magnetic fields beyond the critical strength, covering a regime previously inadequately modeled.

Findings

Spin flip rates are lower than predicted by existing approximations in high magnetic fields.

Equilibrium spin polarization is less pure than previously estimated.

Results are applicable across all magnetic field strengths, including beyond the critical field.

Abstract

We calculate the spin flip rates for an electron in a homogeneous magnetic field for low excitations ($N\le 5$). Our results apply for all field strengths including those beyond the critical field strength at which the spin contributes as much to the electron's energy as its rest mass. Existing approximations either assume that the electron is in a sufficiently highly excited state such that its orbit can be assumed to be classical or the magnetic field be weak compared to the critical field. The regime of high magnetic field strength and low excitations is therefore poorly covered by them. By comparing our calculations to different approximations, we find that in the high field, low excitation regime the spin flip rates are lower and the equilibrium spin polarization is less pure then one would get by naively applying existing approximations in this regime.