Attosecond charge transfer in atomic-resolution scanning tunnelling microscopy

TL;DR

This paper demonstrates the use of attosecond light pulses to achieve atomic-scale spatial and attosecond temporal resolution in scanning tunnelling microscopy, enabling direct visualization of electron dynamics at the atomic level.

Contribution

It introduces a method combining attosecond light pulses with STM to observe electron motion with unprecedented spatio-temporal resolution, bridging attosecond science and atomic-scale imaging.

Findings

Waveform-dependent currents on sub-cycle time scales

Single-cycle near-infrared pulses drive electron wave packets shorter than 1 fs

Atomic-scale imaging of a copper adatom using lightwave-driven currents

Abstract

Electrons in atoms and molecules move on attosecond time scales. Deciphering their quantum dynamics in space and time calls for high-resolution microscopy at this speed. While scanning tunnelling microscopy (STM) driven with terahertz pulses has visualized sub-picosecond motion of single atoms, the advent of attosecond light pulses has provided access to the much faster electron dynamics. Yet, combining direct atomic spatial and attosecond temporal resolution remained challenging. Here, we reveal atomic-scale quantum motion of single electrons in attosecond lightwave-driven STM. Near-infrared single-cycle waveforms from phase-controlled optical pulse synthesis steer and clock electron tunnelling. By keeping the thermal load of the tip-sample junction stable, thereby eliminating thermal artifacts, we detect waveform-dependent currents on sub-cycle time scales. Our joint theory-experiment campaign shows that single-cycle near-infrared pulses can drive isolated electronic wave packets shorter than 1 fs. The angstrom-scale decay of the tunnelling current earmarks a fascinating interplay of multi-photon and field-driven dynamics. By balancing these effects, we sharply image a single copper adatom on a silver surface with lightwave-driven currents. This long-awaited fusion of attosecond science with atomic-scale STM makes elementary dynamics of electrons inside atoms, molecules and solids accessible to direct spatio-temporal videography and atom-scale petahertz electronics.