Modulation of sub-optical cycle photocurrents in an ultrafast near-infrared scanning tunnelling microscope

TL;DR

This paper demonstrates a method for generating and detecting ultrafast, coherent tunneling currents in a near-infrared STM using a novel modulation scheme that isolates carrier-envelope phase effects, enabling high temporal resolution.

Contribution

It introduces a new modulation technique that suppresses artifacts, allowing clear measurement of CEP-dependent ultrafast tunneling currents in STM.

Findings

Successful detection of coherent ultrafast currents in near-IR STM

Effective suppression of thermal and laser power modulation artifacts

Potential for attosecond-scale temporal resolution in STM

Abstract

Lightwave-driven scanning tunnelling microscopy (STM) at near-IR frequencies promises an unprecedented combination of atomic spatial resolution and temporal resolution approaching the attosecond range. To achieve this goal, high-sensitivity optical control and detection of sub-cycle tunnelling currents must be achieved at the STM junction. Here, we demonstrate the generation and detection of coherent ultrafast currents across the junction of an STM illuminated by near-infrared single-cycle pulses. We introduce a novel modulation scheme that avoids time-dependent thermal loading while selectively isolating carrier-envelope phase (CEP)-dependent photocurrents. All artifacts arising from periodic modulation of laser power and thermal coupling are efficiently suppressed, enabling a clean readout of the coherent portion of the ultrafast tunneling current.