Twisted electron in a strong laser wave

TL;DR

This paper explores how twisted electrons with orbital angular momentum behave in strong laser fields, revealing new solutions to the Dirac equation, their dynamics, and potential acceleration methods in intense electromagnetic environments.

Contribution

It introduces non-plane-wave solutions of the Dirac equation with OAM in strong laser fields and analyzes their motion, angular momentum shifts, and acceleration possibilities.

Findings

Existence of non-plane-wave Dirac solutions with OAM in strong fields

Electron motion exhibits classical helical trajectories with quantum broadening

Predicted angular momentum shifts analogous to momentum and mass shifts in intense fields

Abstract

Electrons carrying orbital angular momentum (OAM) have recently been discovered theoretically and obtained experimentally that opens up possibilities for using them in high-energy physics. We consider such a twisted electron moving in external field of a plane electromagnetic wave and study how this field influences the electron's OAM. Being motivated by the development of high-power lasers, we focus our attention on a classically strong field regime for which $-e^2 \bar {A^2}/m_e^2 c^4 \gtrsim 1$. It is shown that along with the well-known "plane-wave" Volkov solution, Dirac equation also has the "non-plane-wave" solutions, which possess OAM and a spin-orbit coupling, and generalize the free-electron's Bessel states. Motion of the electron with OAM in a circularly polarized laser wave reveals a twofold character: the wave-packet center moves along a classical helical trajectory with some quantum transverse broadening (due to OAM) existing even for a free electron. Using the twisted states, we calculate the electron's total angular momentum and predict its shift in the strong-field regime that is analogous to the well-known shifts of the electron's momentum and mass (and to a less known shift of its spin) in intense fields. Since the electron's effective angular momentum is conserved in a plane wave, as well as in some more general field configurations, we discuss several possibilities for accelerating non-relativistic twisted electrons by using the focused and combined electromagnetic fields.