Quantum tunnelling without a barrier

TL;DR

This paper uncovers a novel optical tunneling phenomenon occurring without a potential barrier during strong-field interactions, challenging traditional quasistatic barrier intuition in quantum tunneling.

Contribution

It introduces the concept of barrierless optical tunneling caused by a color switchover in polychromatic fields, expanding understanding of quantum tunneling dynamics.

Findings

Discovery of tunneling event without a barrier at electric field zero

Identification of color switchover as the cause of barrierless tunneling

Highlights nonadiabatic effects in strong-field quantum dynamics

Abstract

Tunneling is an iconic concept that captures the peculiarity of quantum dynamics but, despite its ubiquity, questions remain. We focus on strong-field tunneling, which is vital to all attosecond science. We find an unexpected optical tunneling event that happens when the instantaneous electric field vanishes and there is no barrier. This event arises from a color switchover in a strongly polychromatic field. The tunneling without a barrier reveals the disconnect between the standard intuition built on the picture of a quasistatic barrier and the nonadiabatic nature of the process.