Ultrafast Preparation and Detection of Ring Currents in Single Atoms

TL;DR

This paper demonstrates ultrafast creation and detection of atomic ring currents induced by strong circularly polarized laser pulses, revealing quantum tunneling effects and phase-dependent electron emission with potential applications in attosecond science and topological phenomena.

Contribution

It provides the first direct measurement of how rotating potential barriers affect electron tunneling and phase, enabling control and observation of ring currents at attosecond timescales.

Findings

Transmission probability depends on the magnetic quantum number m.

Electron retains part of its rotational motion during tunneling.

Ring currents can be created and detected with attosecond precision.

Abstract

Quantum particles can penetrate potential barriers by tunneling (1). If that barrier is rotating, the tunneling process is modified (2,3). This is typical for electrons in atoms, molecules or solids exposed to strong circularly polarized laser pulses (4,5). Here we measure how the transmission probability through a rotating tunnel depends on the sign of the magnetic quantum number m of the electron and thus on the initial sense of rotation of its quantum phase. We further show that the electron keeps part of that rotary motion on its way through the tunnel by measuring m-dependent modification of the electron emission pattern. These findings are relevant for attosecond metrology as well as for interpretation of strong field electron emission from atoms and molecules (6-13) and directly demonstrates the creation of ring currents in bound states of ions with attosecond precision. In solids, this could open a way to inducing and controlling ring-current related topological phenomena (14).