Schwinger particle production: Rapid switch off of the external field versus dynamical assistance

TL;DR

This paper investigates how rapid switching of electric fields influences electron-positron pair production, revealing that dynamical assistance with oscillating fields can significantly enhance particle yield, unlike sharp switch-off profiles.

Contribution

It demonstrates that rapid field switching can enhance pair production similarly to dynamical assistance, with detailed analysis of the time scales involved and implications for laser pulse shaping.

Findings

Sharp switch-off does not significantly increase pair production.

Dynamical assistance with oscillating fields can substantially enhance yield.

The enhancement depends on the switching time scale and field parameters.

Abstract

We consider the process of electron-positron pair production in the presence of strong electric backgrounds being rapidly switched on and off and examine the total particle yield. For sufficiently sharp field profiles, the particle number can be substantially enhanced. It is demonstrated that this enhancement is quite similar to the phenomenon of dynamical assistance by a weak high-frequency field superimposed on a strong background. Both these mechanisms are analyzed by means of exact numerical computations, worldline instanton approach, and the locally-constant field approximation. We identify the time scale of the switching profile leading to the pair-production enhancement and argue that the particle yield is highly unlikely to be increased by shaping the switch off of realistic laser pulses. On the other hand, we confirm that it is feasible to observe the dynamically assisted Schwinger effect by adding a rapidly oscillating field to a strong electric background.