Controlling and Streaking Nanotip Photoemission by Enhanced Single-cycle Terahertz Pulses

TL;DR

This paper demonstrates how single-cycle terahertz pulses can precisely control and manipulate photoelectron emission from nanotips, enabling advanced spectroscopic and imaging techniques with ultrashort electron pulses.

Contribution

It introduces a novel method of controlling nanostructure photoemission using enhanced single-cycle THz pulses, combining experimental demonstration with streaking spectroscopy.

Findings

Enhanced or suppressed photocurrent via THz near-field at nanotips

Spectral compression and expansion in electron propagation

Rich spectrotemporal features enabling ultrashort electron pulse control

Abstract

The active control of matter by strong electromagnetic fields is of growing importance, with applications all across the optical spectrum from the extreme-ultraviolet to the far-infrared. In recent years, phase-stable terahertz (THz) fields have shown tremendous potential in the observation and manipulation of elementary excitations in complex systems. The combination of concepts from attosecond science with advanced THz technology facilitates novel spectroscopic schemes, such as THz streaking. In general, driving charges at lower frequency enhances interaction energies and can promote drastically different dynamics. For example, mid-infrared excitation induces field-driven sub-cycle electron dynamics in nanostructure nearfields. Such frequency scalings will also impact nanostructure-based streaking, which has been theoretically proposed. Here, we experimentally demonstrate extensive control over nanostructure photoelectron emission using single-cycle THz transients. The locally enhanced THz near-field at a nanotip significantly amplifies or suppresses the detected photocurrent. We present field-driven streaking spectroscopy with spectral compression and expansion arising from electron propagation within the nanolocalized volume. THz near-field streaking produces rich spectrotemporal features and will yield unprecedented control over ultrashort electron pulses for imaging and spectroscopy.