Loop spin effects in intense background fields

TL;DR

This paper investigates electron spin flip probabilities in intense laser fields, revealing conditions where quantum loop effects dominate over classical radiative processes, with implications for understanding spin dynamics in high-intensity backgrounds.

Contribution

It provides a transparent description of spin dynamics in plane waves and identifies a regime where loop effects surpass radiative contributions, highlighting new quantum effects in intense laser interactions.

Findings

Loop effects can dominate spin-flip probabilities in certain regimes.

Focussed laser fields suppress loop dominance due to geometry sensitivity.

A regime exists where loop effects on spin transitions are potentially observable.

Abstract

Radiative and non-radiative electron spin flip probabilities are analysed in both plane wave and focussed laser backgrounds. We provide a simple and physically transparent description of spin dynamics in plane waves, and demonstrate that there exists a kinematic regime in which the usual leading order perturbative hierarchy of QED is reversed, and non-radiative loop effects dominate over radiative tree-level spin-flips. We show that while this loop-dominance becomes suppressed in focussed laser pulses due to a high sensitivity to field geometry, there is nevertheless a regime in which, in principle, loop effects on spin transitions can be discerned.