Access to Klein Tunneling via Space-Time Modulation

TL;DR

This paper demonstrates how space-time modulation of electromagnetic potentials enables Klein tunneling at much lower energy thresholds than static systems, with tunable transmission properties and potential experimental applications.

Contribution

It introduces a novel method using space-time modulation to achieve Klein tunneling below static energy thresholds, expanding the possibilities for experimental observation.

Findings

Klein tunneling can occur far below static energy thresholds.

A velocity-tunable Klein gap with transmission suppression is demonstrated.

Energy thresholds are reduced by up to four orders of magnitude.

Abstract

We show that space-time modulation of electromagnetic potentials enables Klein tunneling far below the static threshold. The derived kinematics reveal oblique transitions that can connect opposite-energy continua without requiring their overlap, yielding a velocity-tunable Klein gap where transmission vanishes within a finite velocity window and reemerges beyond. The associated reduction in energy thresholds -- by up to four orders of magnitude -- suggests the potential for experimental realization using flying-focus fronts and relativistic electron beams.